Re: Change in EXR open from CS2 to CS3 can this be fixed?

[prog...@adobeforums.com]

well swapping the plugins doesn't work, the plugin wont load under cs3 intel

[prog...@adobeforums.com]

It seems the monkeys have been at the file formats again...!

Open an exr with an alpha in CS2 and the image displays normally and the alpha is retained.

Open an exr with an alpha in CS3 and the alpha channel is applied to the transparency and then lost... which is really STUPID considering you might apply 0 alpha values to parts of the image you retain visually, as you might just want to use the alpha to drive an effect and not just be myopic and think it's just for transparency.

So, can this be fixed? I can't see any info on it?

Will CS2 non intel plugin work on an intel system in CS3

If not, effectively PS is useless for exr work for us.

Or is this fixed in CS4?

[Mike_O...@adobeforums.com]

Great read. Thank you.

[prog...@adobeforums.com]

Yes I do Chris, but alpha isn't transparency. It's an alpha channel. We're importing files with alpha channels, not transparency as generated in PS.

PS might use alpha channels to generate transparency, but it's a bit like saying an RGBA Jpeg should behave the same, yet we know it doesn't. We all know that tga was changed, then changed back again... it's the same thing.

The problem is that EXR is the only format we can convert to from our 3d images, and we like to render in one pass and use the alpha for an an alpha, not transparency. By losing this we now have to render in two passes, one for the RGB data, and another for the alpha, then recombine them afterwards.

CS3 can support both transparency and an alpha in 32 bit at the same time. So can we not have the choice before a file is shredded? At least if we have the alpha we can choose wether to apply it as transparency, or actually use it as a selection to drive an effect. The are a whole host of passes we use alphas for, only one is transparency.

Now it means we have to keep a legacy system around to open EXR's correctly, or render 2 passes. Which is a bit of a bind to say the least considering the size of the renders. Last night it was just the one 50k render. But it took ages to process the 6gb of data to where we need it because we had to chuck it around on old gear.

How much of a hoop is it to add that UI, and how much of a hope that it will happen?

[Chri...@adobeforums.com]

Guido - Photoshop DOES preserve the transparency/opacity data from EXR files, exactly as specified by the file format spec. The only exception was in CS2 when Photoshop did not support 32 bit transparency, in CS2 we just read the transparency channel in as an alpha channel.

If you are trying to use the EXR "A" channel for something other than transparency - STOP. The file format does not allow that. You can add other named channels in EXR, but Photoshop doesn't yet support them.

[prog...@adobeforums.com]

Slightly?

No Chris.

Pre-multiplying is done at the render. It's not something the Exr 'does'.

You cannot un-multiply a render... you have to render it in a different manner completely. It is impossible to un-multiply the image because a pre-multiplied image always contains background data as a % related to the alpha strength. The A is not a by-product of the render's opacity, it is merely a single channel representation.

Photoshop does not just alter "slightly" the files. In your example, if you have a very bright but transparent object, the effect that PS has is to almost entirely remove that image data and the alpha. You cannot get that image data back.

Florian, what PS now does is to take the A and use those values as to generate a selection, and delete from the RGB channels. So if you A value is black, areas are entirely deleted, if the value is 50%, 50% is deleted and so forth. And it does this automatically, and so the image is destroyed, and the alpha is lost.

On the other hand, this would be less of an issue if PS guaranteed that RGBA data pass through unaltered unless the user
explicitly modifies the image.

Exactly correct.

If people are having trouble seeing what the problem is, let me know and i'll post some examples tonight.

[Floria...@adobeforums.com]

Chris, and Progress,
I guess I don't understand what Photoshop does with OpenEXR's A channel.
When you open an EXR image with RGB and A channels in PS, and then
immediately save the image, will the new file not be identical to the original?

[prog...@adobeforums.com]

Thanks Guido, it helps to know it's not just us little chaps having trouble.

Perhaps you can split your alphas off before PS get's to it?..

I'm not sure we can with our renderer... we might have to get it to render RGB, then again for the alpha. For standard alphas that's a hoop jump, but if we wan't shadow matte in the alpha for example, then thats a big pain as it effectively means we'll be getting close to doubling our rendering times... and we normally work on 8k+ renders, so that's a bit of a nause.

[Chri...@adobeforums.com]

Progress - read Florian's statement and the EXR spec. again. His "A" is defined as transparency. The explanation is just confused by referring to it as alpha (which could be any additional channel, not just transparency). But the math, and the requirement for premultiplication means it must be transparency. That is the only interpretation available, and the interpretation that Photoshop uses.

Yes, premultiplied transparency does lose image data -- but that is the way the EXR format is defined. Your "nuking" happened when you saved the EXR file, because it has to be premultiplied (transparent areas go to zero in the color channels).

The only change Photoshop makes is to un-multiply the data, because Photoshop does not work with premultiplied data. The data is re-multiplied when you save the file, resulting in no net change to the file data. Transparent EXR files round trip just fine through Photoshop, as far as I can test with files from ILM, or those that I have created.

If you wish to have an arbitrary alpha channel (one not treated as transparency) in the EXR format, you will need a third party plugin. EXR does allow for extra channels, but the Photoshop EXR plugin does not support them yet.

[Floria...@adobeforums.com]

Chris,

In an EXR image it is legal to have pixels with non-zero RGB values
and a zero or nearly zero A value. Such a pixel represents an object
that emits light but is otherwise transparent, for example, a candle
flame. (If you place a candle between a bright light source and a
screen, the flame casts no shadow.) In this case un-premultiplying
leads to infinite or very large RGB values.

Chris, I agree with you, the A channel should be used for alpha (in
the transparency sense). I don't see how PS could possibly guess that
A is in some files really a depth channel. That's why EXR supports
arbitrary channels, and why the specification recommends using Z for
depth. On the other hand, this would be less of an issue if PS

[prog...@adobeforums.com]

Chris, I think your wrong on this. I think that's backed up by TD's from Pixar and the originator from ILM posting as such. It's being interpreted in the wrong manner, ie assuming transparency = alpha.

Exr doesn't have transparency in it's spec. Its RGB+A. But PS is presuming that A = Transparency. Not only that, it's applying it and deleting it before the file is viewed, which means when it's used in pre-multiplied it's actually taking away image data that can't be put back.

It's not done with any other format, and it's not done with tga now it's been changed back. It's the very same thing.

PS is making irreversible changes to the document when it's opened. It doesn't matter even if later you define the alpha as the transparency, it's nuking the image that's the problem. Pre-multiplied means that for any pixel value except 0 in the alpha, the alpha will remove some of the image + the background it's "transparent" against.

If I have an alpha, I can choose to apply it to the image to make transparency as I wish.

It's impossible to rebuild an Exr back to what it was once PS has got hold of it, because by applying the alpha as transparency it has deleted RGB image data.

A 1/2 way house would be to have it as a layer mask... at least then both your transparency interpretation and the image data is retained and the user can have the choice.

[Chri...@adobeforums.com]

The color channels may be altered slightly due to un-multiplying and re-multiplying (remember: Photoshop does not use premultiplication, so we have to un-multiply to use the image). So, the least significant bits may change.

[Buko]

start CS3 in Rosetta and the plugin should work.

[Floria...@adobeforums.com]

Hi Chris,

with OpenEXR it is standard practice to interpret the "A"
channel as pre-multiplied alpha. Compositing a foreground
layer over a background layer is correctly done like this
(see <http://www.openexr.com/TechnicalIntroduction.pdf>, page 5):

composite = foreground + (1-alpha) * background

Programs that read and write OpenEXR files generally adhere
to this convention. I don't know how transparency works in
Photoshop; your message suggests that PS transparency is not
the same as alpha. This would imply that PS should not treat
OpenEXR's alpha channel as if it was transparency. Of course,
PS could add transparency channels as needed when it writes
OpenEXR files.

Florian

[Chri...@adobeforums.com]

CS2 did not support transparency in 32 bit/channel, thus could not show transparency in OpenEXR documents, and so opened the transparency channel into an alpha channel.

CS3 does support transparency in 32 bit/channel, uses the transparency data from OpenEXR documents, and opens the transparency channel as transparency.

This can only be fixed by adding UI to the OpenEXR plugin "Do you really understand that transparency is transparency?".

[Chri...@adobeforums.com]

Florian - you are confusing the terms alpha (any extra channel) with transparency (what you called alpha). Photoshop reads and writes OpenEXR files exactly as you stated - with premultiplied transparency.

Apparently some users thought EXR supported general alpha channels and are now confused when those channels are treated as transparency (as the file format specifies).

[prog...@adobeforums.com]

For us, it's not that it doesn't behave the same, it's that you often dont want it to, and alpha isn't always transparency. We might use it as a matte or z-buffer.

It looks like with another hoop jump, we can strip out the alpha before PS gets its sticky mitts on it and assumes it's an alpha for transparency before we tell it wether it is or not.

[Guido_...@adobeforums.com]

This is a huge deal for us (Pixar) as well. We are trying to integrate (finally) OpneEXR into our pipeline and when I load OpenEXR files with alpha computed by the renderman, it gets lost in Photoshop CS3/CS4.
Now the option here is to either ask Adobe to fix this in CS4 and allow an option at the loader level or we have to write our own OpenEXR reader.
To better understand since I don't get the difference between transparency and alpha (for us, we just deal with alpha) how the OpenERX file should be structured so that we can retain the alpha/transparency from the file ? Maybe we can modify the renderman driver.

thanks,
guido

[Chri...@adobeforums.com]

Alpha Channel - any extra channel beyond the color channels. This has nothing to do with transparency (except as a historical footnote). Anything can be stored in an alpha channel, it does not have to be related to the color channels at all. You can have many alpha channels in an image.

Transparency - a subset of extra channels, closely related to the color channels, with special meaning. Can also be called Opacity (transparency and opacity are the reverse of one another). You can only have one transparency channel in an image. This may be premultiplied with the color data, depending on the file format specification.

[Chri...@adobeforums.com]

Progress - yes, you can un-multiply (aka divide with appropriate handling for zeros)! You have to in order to bring a premultiplied image into an app that doesn't work with premultiplied data. We do it all the time with file format that specify premultiplied data (like TIFF). Premultiplication does not necessarily happen at the render stage - it may, depending on the renderer, but in many cases it is an explicit step since some file formats want premultiplied data and others do not.

And your description of what Photoshop does with the transparency channel of EXR files is very, very wrong. The transparency is not lost in any way (assuming you are using CS3 or CS4 extended, since the standard version does not support 32 bit transparency/layers/compositing).

Photoshop cannot "pass through unaltered" because the file format is premultiplied and Photoshop doesn't work with premultiplied data. We have to undo the multiplication. Then the file format requires that it be multiplied before saving.

[Chri...@adobeforums.com]

And it looks like Guido's problem was some people using extended, and other people using standard (who could not see the transparency correctly, because standard does not support 32 bit/channel transparency).

[prog...@adobeforums.com]

What Exr is doing is applying the A into the image and not making it editable...althought the transparency is applied, the transparency is effectively "lost" because it cannot be got at.

Another point that you might not be aware of is that the RGB data is built from the RGB of the object against the background. The background might often contributes nothing to the alpha, but does to the RGB... so when the alpha removes the area it removes RGB data. Obviously this is exagerated when using pre-multiplied values of not 0 or 255, because it removes a proportion of the RGB (including the background) related to the A value.

Because of the way PS can't handle pm, it is the exact reason why it shouldn't assume alpha isn't transparency.

If I render an object with no transparency with the values 128,128,128 and A=0 then render it with 50% opacity, the image is 128,128,128 and A=128. The problem is that although the pixel values are stil 128 in the RGB, the image is transparent! You can't get that "solid" 128 RGB data out because PS ties it's transparency in with it... you can't unhook the two apart from each other. There's no layer mask to lose, or alpha, it's 'baked' the transparency into the image...

It's not so much that the transparency is lost, it's that the image is irrevocably broken... I can re-generate an alpha from the transparency... i can't see how i get those pixels back to full opacity though.

perhaps there is a way of doing it... how do I get a that image back solid? The pixel values haven't changed, they're still 128, 128,128... the alpha is gone, there is no layer mask, the layer is 100% opaque... yet there is a transparency value attached to each pixel that I can't get at.

The only way I know how is to put the exact colour in the background that was used in the renderer... but it might not be a colour used as the background, it might be an image... it might be a background plate which normally carry no alpha contribution... that's the problem.

You don't arbitrarily apply transparency in 8 or 16 bit to other formats before they are opened... why do it in 32 all of a sudden? They all support transparency once in PS (well its PS that supports it, not the format)... same as Exr.

In fact, it was this exact problem that prompted the backstep on alpha. I can't see why you can't see this as the same thing, because from our end it is.

If you want Chris, I can send you the exact files. A simple transparent box floating over a background, rendered. Normal alpha generated from the opacity straight from the file. All standard stuff, straight from a standard renderer. Your challenge is to tell me what was in the background. Your 2nd one will be to re-create it. With the CS2 you can... with CS3 you can't.

It's broken.

But does this mean we can load the CS3 non extended plugin in, or does the app do the damage? Could that be perhaps made available if it solves the problem?

[Chri...@adobeforums.com]

Progress - no, it is not broken, it is working exactly as intended, exactly as the file format spec. says it should.

In the openEXR file format, the "A" channel is defined as transparency/opacity, and the color data must be premultiplied with that transparency/opacity channel.

If you render an image with transparency/opacity into OpenEXR, Photoshop will open that image with transparency/opacity - exactly as the file format spec. says it should.

Many file formats include transparency/opacity and are premultiplied (like TIFF), and we have been handling them exactly the same way since Photoshop 3.0. There has been no change - we have to treat transparency/opacity as transparency/opacity.

With CS2, it was broken - because 32 bit/channel did not support transparency or layers (they are connected). So, in CS2 (and Photoshop standard) you get the same result as if you'd opened a transparent TIFF back in Photoshop 2.5 -- the color data, with transparency stored in an alpha channel (because we had no way to display or use the transparency).

Your description is very confused, so I'm not really sure what you are trying to accomplish. But the OpenEXR support is working exactly as it must work.

[prog...@adobeforums.com]

Chris, it's not. It's really simple.

If I open a tiff with a premultiplied alpha it stays as RGB and A. No transparency is seen.

If I open a targa with a premultiplied alpha it stays as RGB and A. No transparency is seen.

If I open a jpeg with a premultiplied alpha it stays as RGB and A. No transparency is seen.

Yet if I open an EXR with a premultiplied alpha it removes A and applies it to the RGB. It doesn't alter the RGB values but it adds a transparency value that PS understands but is not editable.

Thus with PS's handling of transparency, I now end up with transparency embedded into the file which cannot be edited.

It must work another way because CS3 Standard and CS2 previous work another way. Just because 32 bit in CS3e supports transparency does not mean the A should be applied to the image to produce it. Just like it doesn't for every other format in 8 & 16 bit, which also support transparency.

I'll make it clear... PS deletes RGB image data based on alpha values. That is not correct. No other format does this. And this is why Targa had to be changed back. Because it was an incorrect interpretation of what an alpha is. An alpha is not transparency, it's a greyscale representation of transparency. There is nothing in the EXR or other format that says it has to be applied to the RGB image, and since other formats dont behave the same way I don't see why Exr should either.

It's so VERY VERY broken. Do you think I would bother posting here if there was no effect on the image?

Or am I missing something fundamental that allows me to retrieve RGB data from the file which has been made transparent, even though there is no layer mask or alpha?

Is the plugin different on CS3 standard? Or is it the code in the extended application that adopts a different interpretation.

[Chri...@adobeforums.com]

Progress - it really is that simple.

If you open a TIFF with transparency, Photoshop shows transparency - otherwise the TIFF file was written incorrectly (something certain 3D apps mess up from time to time) or you wrote the extra channel as an arbitrary alpha channel. TIFF does support transparency/opacity and arbitrary alpha channels.

TGA should support transparency, but we backed off because so many people were misusing the file format. We still have people who want to open it one way and save it another (meaning we should prompt for how to handle the fourth channel at open and save).

JPEG does not support transparency at all.

The transparency/opacity in an EXR file is not lost - it's right there as transparency/opacity. Where it is supposed to be. Nothing is removed. Nothing is deleted. Oother file formats that support transparency/opacity work the same way. Other file formats that are premultiplied work exactly the same way.

CS2 was just broken with regard to 32 bit transparency. CS3 standard tries to follow the CS2 path because it also does not support 32 bit transparency. But CS3 (and CS4) extended are working exactly as they must work.

Look: transparency/opacity is transparency/opacity and must stay transparency/opacity. If you want to use that extra channel for something other than transparency/opacity - use another file format that supports that concept. Right now you are either hopelessly confused about the concept, or just using the wrong file format to do what you are trying to do.

[Floria...@adobeforums.com]

I find this discussion very confusing. Does anyone have an example,
say, an EXR file with alpha straight from a renderer and the same file
after it has gone through PS?

[prog...@adobeforums.com]

I will post examples if i have time this week, if not next.

Chris, if you open a tiff with an alpha, it does not display transparency. It displays RGB and an Alpha. Even if you save it with an alpha, it opens back up with an alpha.

However, I can introduce transparency and save it as that as well as the alpha.

So what is different then? If alpha must equal transparency, why doesn't tiff behave the same. Moreover, why can we have a transparency and a different alpha in the same document, yet the two are apparently the same? That does not make sence in relation to your point of view.

Targa, as Adobe found out, was changed to be wrong. Adobe interpreted it in one way, and the rest of the digital world told Adobe why it was wrong. This is largely the same. It's broken/wrong.

[Chri...@adobeforums.com]

alpha != transparency -- they are not the same and the terms have not meant the same thing in over 20 years.

Progress - remember, alpha can have multiple meanings (arbitrary alpha channel, or transparency/opacity). Please be clear about which meaning you are using. If you mean transparency or opacity, say so. If you mean some extra channel that has no relation to the color channels (alpha channel), say so.

TIFF can contain transparency/opacity AND/OR arbitrary alpha channels. If you have a TIFF with transparency/opacity, then the TIFF will open with transparency. Some 3D packages have bugs in their TIFF support where they fail to mark the transparency channel as transparency, so it opens as an alpha channel instead.

OpenEXR does not support arbitrary alpha channels, only transparency/opacity.

LOL! TGA was changed to follow the spec. Some users were using it incorrectly. So we changed it back to NOT following the spec. It's still maybe 60/40 on the usage of TGA, and we get complaints from both sides.

OpenEXR is implemented correctly in Photoshop, exactly as the spec. says it has to be implemented.

[Floria...@adobeforums.com]

I loaded the Blobbies.exr file from the OpenEXR sample image collection
into Photoshop CS3. The file has an A channel (the kind that PS calls
"transparency" and most other people call "alpha").

I used the paintbrush tool to paint onto both transparent and opaque
areas of the image, and I used the eraser tool to create holes in the
opaque areas. Then I saved the result in another EXR file and looked
at the file's R, G, B and A channels with exrdisplay. The data in the
file were what I expected: the paintbrush had moved the A values closer
to 1.0 and the eraser had moved the A values closer to 0.0. The RGB
values seemed to have been properly premultiplied with A. Compositing
the painted-on image on top of another image in PS also produced the
expected results.

As far as I can tell Chris is right, PS handles OpenEXR's A channel
correctly. What am I missing?

The case where A is zero and R, G and B are not zero means something
inherently different in PS and EXR. PS could probably do a pretty good
approximation of the EXR semantics by clamping EXR's A to the range
[1e-9, 1] before un-premultiplying. For all practical purposes an A
value of 1e-9 is zero, but it would allow PS to preserve non-zero
RGB values and to un-un-premultiply on save.

[prog...@adobeforums.com]

"As far as I can tell Chris is right, PS handles OpenEXR's A channel
correctly. What am I missing? "

Depends on what you open it back up in. Open it after saving out in PS Extended again and you'll see that the A channel has gone, and the opaque areas are now holes (perhaps how you left it) So you can no longer edit the A channel except destructively, by adding even more transparency. You cannot reduce the transparency.

After saving the image with holes, open it back up again in PS and try and paint back in opacity on the A channel, without affecting RGB at all. I could do this before because I had direct access to the alpha. With the alpha seperated as before I can adjust the A without affecting the image's RGB. Not only that, I don't lose areas set to black on the alpha from RGB when it opened. I now do. They are removed, as per holes.

Before, if i received an image with a background that would be removed by alpha when applied, I didn't need to know what that background was... now I do because it's removed before I can see it.

I will post links later this week hopefully when I have time.

There is a fundamental difference between the two behaviours. The latter removes functionality in a very big way.

[Chri...@adobeforums.com]

I think what progress wants is for the "A" channel to open as an arbitrary alpha channel so he can edit it directly.

But OpenEXR defines "A" as transparency/opacity - and you can't easily edit transparency/opacity data in Photoshop without editing the color data as well.

And because OpenEXR is premultiplied, there may not be anything to work with in the transparent areas anyway.

Again, he's using the wrong file format for what he's trying to do.

[Kri...@adobeforums.com]

Progress: I so agree with you. I sit on OpenEXR images that are currently useless right now. I don愒 care if the alpha channel is transparency or not - I just want the possibility to edit that channel. Now I can愒!

OpenEXR is the right file format for me as it supports high dynamic range and is (was) great for renderings. I could choose TIFF too but it愀 the same problem there. The alpha is applied and the channel removed. My previous workflow was smooth when I could include the alpha directly into the file instead of render two files for every image.

It worked in the previous Photoshop versions so why change the plugin now?

[Chri...@adobeforums.com]

Yes, if you specify transparency/opacity in the file, Photoshop will open that file with transparency/opacity. That's what it is supposed to do. The channel is not removed or applied - it is right there in front of you!

The OpenEXR plugin was changed in CS3 because CS3 was the first version to support 32 bit/channel transparency. Photoshop CS2 supported OpenEXR and 32 bit images, but not transparency. That means that OpenEXR support was broken in CS2, and was fixed with CS3.

In short - it did not work in previous versions, and your problem (wanting to edit transparency data directly) has little to do with the file format. You relied on a bug (or lack of a feature) to do something unnatural for that file format.

[Floria...@adobeforums.com]

Chris, I guess we have established that Photoshop does
The Right Thing (TM) when opening an OpenEXR file with
an A channel or an equivalent TIFF file. On the other
hand, the request for an option to open the EXR A channel
as a PS alpha channel for independent editing sounds
entirely reasonable. I guess progress is requesting a
new feature.

Progress, if you use the OpenEXR A channel to store
information other than how transparent a pixel is, then
how is software such as Photoshop supposed to know when
the A channel really is an A channel and when it is, say,
depth by another name? If you are storing depth in the
file, you should probably call the depth channel Z as the
EXR documentation recommends.

You can ask Renderman to split the output of a single
render pass into multiple files if packing all the output
channels into a single file is inconvenient. You can,
for example, have Renderman write two EXR files, one
with the R, G and B channels and one that contains only Z.
This way you can edit the RGB image in Photoshop without
altering or even loading the Z channel.

[Floria...@adobeforums.com]

Progress and Krille, this Photoshop plugin may be just what you need: <http://www.fnordware.com/ProEXR/>

[prog...@adobeforums.com]

Thanks for the link Florian.

I've probably complicated the conversation by the suggestion that A be used for something else. The ability to use A as non transparent information is a bonus, but even the ability either edit A or simply for A not to be directtly translated into transparency would be great.

The simple problem is that elements such as background info might be specified quite normally as black in the alpha, then these are lost when opened. PS is deleting data created. I know it's only applying transparency, but it's not editable. I can't get to the data before PS deletes it.

PS treats data that is 100% transparent as 100% redundant. It isn't. I might want to get to that data.

Could it be done so it opens as a layer mask instead? Then both camps would be happy then.

(I guess there are work arounds, but I can't help thinking there's no good reason that A should automatically be converted into transparency)

[prog...@adobeforums.com]

Chris, does the difference of how transparency is handled between extended and normal PS mean the plugins are different?

[Chri...@adobeforums.com]

Note to self - go write a plugin to copy data out of transparency and into a layer mask. The reverse is already available with "apply layer mask".

[Chri...@adobeforums.com]

Progress - The extended and standard behavior is just a switch in the code, not different code. It just does slightly different assignments based on the host licensing.

And again-- Photoshop is not deleting any data. Your only problem here is that you want to edit the transparency/opacity data directly, and Photoshop does not let you do that easily. Opening the transparency as a layer mask adds some serious problems with roundtripping and compatibility with other file formats (because most of them do not support layer masks).

"A" in OpenEXR _is_ transparency. That is the way it is defined, that is what it must be. Using that channel for anything else breaks workflows (which is why I hate putting it in an alpha channel in standard).

[prog...@adobeforums.com]

If the last post isn't sarcastic, then that would be a very useful solution to a number of scenarios where transparency is embedded and prevents RGB editing of data hidden by a transparency which is not editable.

I still maintain that A isn't transparency, but a representation of transparency... but i'm willing to drop the pedantry if it gets us somewhere.

[Chri...@adobeforums.com]

In OpenEXR "A" is defined as transparency/opacity. And OpenEXR is premultiplied - so anywhere you had "A" set to zero -- the matching color data is gone.

[prog...@adobeforums.com]

But it isn't "gone"! Because if I open it up in CS2 it's there! Along with an intact A. That's my whole point. Arghhhhh! It's still transparency, because I can invoke that when I choose, without losing data...

It wasn't gone on save. It's not gone on open in anything else but CS3e. It's only gone because of the way just CS3e handles it. It's only "gone" because CS3e hides it, and it's effectively deleted as you can't unhide it. Actually, it's still very much there, except that CS3e stops you getting to it. You can even save it out and find it again in CS2!

It's not anywhere just where A=0, it's anywhere where A doesn't = 255 because it's pm'd the value will remove a proportion of the colour data based on it's 0-255 value.

Do you not see what the problem is?

Now, if you can reverse or "ungone" the info, then great...

Or is there a way to downgrade an install of CS3e to CS3 (to avoid hoop jumps elsewhere..?)

[Chri...@adobeforums.com]

Premultiplied color/alpha/transparency means file_color = color * opacity
Where the opacity was zero, the information is *gone* after it gets written into the file, not recoverable, pining for the fjords... (er, wrong sketch, sorry).

The problem is that you are trying to use a file format that doesn't support what you're trying to do, plus you're trying to edit transparency/opacity - which Photoshop doesn't let you do easily.

[prog...@adobeforums.com]

Where the opacity was zero, the information is *gone* after it gets written into the file

But it isn't ! If I open the original EXR up in CS2 it's there. Along with the alpha. IT HAS NOT BEEN REMOVED ! :D

Only if i throw it into CS3 then out again and open it in CS2, is it removed. So that must mean? That must mean PS is changing the file... ta dah...! See the problem?

which Photoshop doesn't let you do easily.

which should read ;

which Photoshop did let you do easily, but has been broken.

[Jonah...@adobeforums.com]

Just to chime in here and back up what progress is saying. CS3 and CS4 have ruined EXR Alpha functionality. We had to buy ProEXR from Fnord in order to keep the RGB values of the black Alpha pixels.

In the ProEXR installation instructions they have you rename the Adobe OpenEXR.8bi to OpenEXR.WTF

I think that says it all.

If this discussion were a tech support call, this is the point where I would give up and ask to speak to the manager.

[DAVID_...@adobeforums.com]

Ditto to what progress and jonah have said...openEXR simply does not work in it's current implementation in CS3 (& CS4). I've read through the EXR description on ILM's site and I don't see anywhere that it requires the RGB to be made transparent due to the alpha. Yes, they do describe the pixel as being transparent, but this is in relation to performing any compositing actions, not opening it for editing.

Regardless, can you just add a tickbox option somewhere to allow photoshop to open OpenEXR's as RGBA rather than a transparent RGB?

[jonah]

Chris,

Please open an EXR in CS2, to see what we are talking about.

or After Effects, any version. go to Interpret Footage and choose ignore alpha.

In a 3d app like 3ds Max or any other, it is common to render an object against an environment or background image. By default the 3d geometry has a value of 1.0 in the Alpha channel and the environment 0.0. But this does not mean we ALWAYS want the environment to be transparent. Many other file formats retain the Alpha RGB values. As did EXR in Photoshop CS2. I'm sure you're aware of the Alpha present in Targa, Tiff, RLA, PNG, etc.

All we want is the option to keep the RGB of the Alpha. Just like it was in CS2.

Small change to your plugin has a huge impact on our workflow.

[Chri...@adobeforums.com]

David - you're so unclear on the concepts I don't even know where to start.
That entire post is a non-starter.

[Chri...@adobeforums.com]

SIgh - just when I got the original folks to understand....

Please, go read the rest of the thread.

Here is the summary:
RGBA *is* RGB+transparency in the case of OpenEXR - the file format says that it must be that way. The file format does not allow you to use the A channel for anything other than transparency. And the file format says that the RGB values are premultiplied (that happens when you write the file) -- so if you have zero in the A channel, you must also have zero in the RGB channels.

Most likely you misunderstand something about the concepts involved, or you are just using the wrong file format for your work. But, as far as anyone has been able to determine, Photoshop CS3 and CS4 are working perfectly correctly for the OpenEXR file format.

[Chri...@adobeforums.com]

jonah - I have. I've also discussed it with the folks who wrote OpenEXR (the spec. and the code). Photoshop has it right.

[Kri...@adobeforums.com]

Florian, thank you for the link! Finally someone who brought the "bug" back so I can edit my images "illegal" again.

[DAVID_...@adobeforums.com]

Whatever Chris. I'm not an engineer/programmer but I don't see why you still can't have an option when opening exr's to open them using the CS2 convention of RGBA rather than transparent RGB. Is it that hard?

[DAVID_...@adobeforums.com]

Also, since you seem so intent on adhering to the openEXR spec, where's the support for the rest of the file format features:

-alpha; luminance and sub-sampled chroma channels; depth, surface normal
directions, or motion vectors

-Multiple versions of a tiled image, each with a different resolution, can be stored in a single multiresolution OpenEXR file

-color timing information, process tracking data, or camera position and view direction. OpenEXR allows storing of an arbitrary number of extra attributes, of arbitrary type, in an image file.

[Cliffton....@adobeforums.com]

Chris,

I second everything progress, jonah and David Parisi are saying.

How can discarding the A channel possibly be the correct way of opening an EXR file? And if discarding the A channel is correct according to ILM, then AE, Combustion, Nuke, Fusion are all wrong?

And in a file format that allows one to save multiple channels as described by David Parisi, how does discarding the A channel make any sense? If the proEXR plugin allows one to access multiple additional channels, including the alpha channel, are the proEXR guys doing it wrong as well?

AE has now adopted portions of the proEXR plugin which allow access to additional channels in the EXR format. Why would Photoshop refuse to accomodate such added functionality? What if Photoshop adds multiple channel access in future releases? Will they still discard the alpha channel?

[Chri...@adobeforums.com]

David - we can't have the option, because the file format does not allow the option, and the specifics of the file format make the option pointless in the first place.

PLEASE go read the existing thread. We've been over this. Your questions have already been answered, multiple times, in excruciating detail.

And no, we haven't implemented all features of the OpenEXR file format yet. Most people aren't demanding all the extras, some of the extras don't fit in Photoshop, and they're adding more niche stuff all the time.

[Chri...@adobeforums.com]

Cliffton - Photoshop does not discard anything. We read the transparency channel just like the file format says we are supposed to. The A/tranparency/opacity channel is right there in your document, doing what it is supposed to do.

Yes, ProEXR is wrong for allowing you to open the A channel as anything other than transparency (especially if they fail to handle the premultiplication).

It sounds like you really don't understand the terms and technologies involved, and you also need to go read the existing posts in this topic.

[DAVID_...@adobeforums.com]

Chris-Why doesn't the file format allow for the option? It seems like you did it in CS2 and CS3 Standard so why won't it work in CS3 Extended. Isn't the file format the same in both? It seems the only thing different is the import code, not the file format.

Where's the other "existing" thread where you explained it all? Do you mean the rest of this one?

[Chri...@adobeforums.com]

David - please read the existing posts in this topic.

[Cliffton....@adobeforums.com]

Thanks for clearing that up Chris. You might want to tell your colleagues developing AE that they are doing it wrong as well.

[jonah]

WOW. Too many hours a day coding Chris? Not enough sleep? Right about the time that Guido Quaroni from !!!!PIXAR!!!! chimed in, I would start listening buddy!

If I were on the phone to tech support, this is the point in the conversation where I would ask to speak to the manager! :D

Joking, joking.

I have read all of this discussion. I understand the math: color * opacity. But many other apps give you the option to ignore the Alpha thus keeping the RGB.

I've made an EXR in 3ds Max <http://www.jonahhawk.com/EXR/Alpha.exr>

Ok, to help illustrate our point further, please open it in After Effects. Right click on the EXR footage and choose Interpret Footage. Choose Ignore under Alpha Channel. Viola! the RGB data is intact!

If this doesn't help you understand where we are coming from maybe you could have someone else discuss the issue with us. I can tell you are getting frustrated.

[Chri...@adobeforums.com]

Jonah - Guido and I go back a ways. And Guido's problem turned out to be someone not understanding the difference between Photoshop and Photoshop Extended (different people had different versions, leading to increased confusion). I believe he's got it straightened out now.

OpenEXR is a format where you can't just ignore the A/transparency/opacity channel - because the format defines that channel to be one thing and one thing only, and ties it closely to the color (by making it always premultiplied). If you want flexibility, you may need to use a different file format.

Ignoring the file format spec. leads to workflow problems, interoperability problems, etc. And it seems a few people have already started OpenEXR down the road to ruin by either not understanding the file format (or even the terms involved), or trying to make it do things it is not intended to do. I know it might be expedient -- but nobody is going to be happy if you keep using that screwdriver like a hammer.

[jonah]

Ah, so you did open that EXR in AE then? why is the rgb still there in AE?

So the few people who...

"have already started OpenEXR down the road to ruin by either not understanding the file format (or even the terms involved), or trying to make it do things it is not intended to do"

include the developers of After Effects, Nuke, Fusion, etc...Photoshop is now the anomaly in our workflow.

Targa and tiff files work this way but neither of these will store extra channels like Z depth, Velocity, Object ID etc. This is why we love EXR.

I really don't understand why you won't admit that having the option is better than not having it. Let us wallow in file format blasphemy if we so choose!!

Have you done any compositing work yourself? Have you tried opening the EXR file I posted in After Effects and seen what happens when you choose ignore alpha?

[Chri...@adobeforums.com]

TIFF can store extra channels, and more standard metadata than EXR.
TIFF can have transparency and unassociated alpha channels.
TIFF will also be premultiplied if you include a channel as transparency, or not if you save the channel as an unassociated alpha channel.
You might want to learn more about the file formats you use.

An option that goes against the design of the file format, breaks interoperability, and still won't do what you think it will do -- is just pointless. It's like asking for a "read it backwards while standing on one foot" option -- silly, and won't really help you accomplish your task.

And just because someone else included a bad option in their application does not mean that other applications should make the same mistake. ("hey kids, let's all jump off a bridge!")

If OpenEXR changes their file format specification, we'll reconsider. But right now the file format as specified means that implementing your request would be both damaging and misleading. (and the fact that you don't understand the damage makes it scary misleading...)

Um, I write the file format code, I write the composting code, work with the standards groups, work with the visual effects industry, and I use everything that I write. I probably do more compositing before lunch than you will do all year.

[Neil_...@adobeforums.com]

Chris,

I write the composting code

Had to laugh here. I assume you mean "compositing".

Neil

[Chri...@adobeforums.com]

Darn spiel cheekier doesn't always catch my typos.

[Neil_...@adobeforums.com]

Chris, I can fix that typo, if you wish, but -- it IS good for a laugh, you must admit!

Neil

[jonah]

wow. good thing you write code and are not in customer service!

So you ARE saying that After Effects, Nuke, etc are all doing it wrong?

[asa_h...@adobeforums.com]

Ill agree with those here in the vfx industry who are asking for this functionality. We need options, albeit with the reasonable defaults Chris is talking about.

We use unpremultiplied imagery like this often in certain circumstances, and we know we are not the only ones. Nuke and Shake and Fusion all do not force you to be premultiplied or unpremultiplied, making you have to handle all this yourself. Being able to be smart about how we make our file import interpretations allows flexibility. If you want to paint a mattepainting for reprojection onto cg, you may want to start with the painting first, and then start to hack away(make transparent in the final render) parts while you go through the iterative development process. If you eat in too much by painting black on the alpha and you have saved it, you want the ability to go back and "undelete" that area. The alternative now is to have a psd master file with a layer mask, and then bake down an rgba version every time you make an edit, this adds an additional file and management to something which could be simplified by adding this import/saving behavior option. If AE has it why can't photoshop have it?

[Ramón_G_Castañeda@adobeforums.com]

If AE has it why can't photoshop have it?

If you keep pushing it, it might well disappear from AE. :D

[Diogo_...@adobeforums.com]

Even tho I have the feeling that this discussion won't get to any conclusion, I have to say that I find that the way PS is dealing with EXR Alpha channels is just plain wrong.

Baking the contents of the Alpha channel into the RGB transparency makes it impossible to work with un-premultiplied RGBA images, especially output them from PS.

If you render a TIFF with RGBA channels and you open it in PS you get a "Background" and "Alpha 1", both untouched as it should be since I can add (or not) the transparency to the RGB channels at any point in PS as I please. This is the right way since PS isn't guessing if my RGB channels are pre-multiplied or not, nor if I need transparency or not. It leaves that decision to me, which is a smart thing to do since I'm the one who can judge what I'm seeing and what are my exact needs.

But if you render the very same file in EXR format with the very same set of channels of the TIFF (RGBA), when you open it in PS you get "Layer 0" and no Alpha channel.

This is just plain wrong since PS is assuming that the RGB was premultiplied by A, and that the RGB transparency is required (desired) by the user. Something that it shouldn't do no matter what the files specs say or don't say. That's an action that should be taken by the user since as far as I know computers don't actually have a visual awareness of the images they are processing nor are aware of the context where they will be used.

Alpha which as far as I know is usually used as a RGB matte channel is indeed intended to be a "transparency channel" but that doesn't mean that a application (PS in this case) has the right to trash my RGB data just because it "makes sense".

Photoshop as image editing (retouching app) should keep it's premise of being able to open - edit - and output an image with no data being lost or being drastically changed from input to output, period.

Being able to retain data as it is throughout the process is a must and a basic necessity in any digital workflow that I know of.

cheers,
dg

[Alan_...@adobeforums.com]

Chris, I'm a bit surprised by all the confusion in this thread. I'm not sure that it's intended, but you're coming across as the kind of Adobe engineer who we've always been frustrated by in the past. When it comes to EXR, Adobe is in no position to be redefining established workflows. Please look at how it is used in Nuke, which probably has the deepest implementation in the industry, with millions of frames processed. Many of us are sick and tired of the contortions we've had to go through in order to make Photoshop fit into established VFX workflows over the years, and we've held out hope that Adobe might finally get it right now that Photoshop has broad support for 32 bit float.

Alan

[gary_...@adobeforums.com]

Chris-

there is a reason AE added an "interpret as linear light" option. Those scoundrels in the AE team actually listened to the testers and, while it's unconventional to represent exr rgb data as gamma encoded, it does happen. If users want it, it might be worth considering.

gary

[Ean_...@adobeforums.com]

Hi Chris,

Like Alan said, I think "contortion" is quite a good word to describe the experience me and my colleagues had while fitting Photoshop into our Nuke-based vfx compositing pipeline for a major studio just a few months ago.

And reading through this entire thread... I'm exhausted by it. Please please listen to Progress, David, Jonah and Alan etc. Can we get a little flexibility here with PS's EXR behavior?

Or is this an exercise in squaring the circle? :(

Cheers,
-Ean Carr

[Chri...@adobeforums.com]

If you use OpenEXR with an A channel (defined as always being transparency) then you ARE working with premultiplied data. Even if you work with it unpremultiplied while in the application (like it always is in Photoshop) - you already premultiplied it when it went into the EXR file. YOU ALREADY LOST DATA WHEN YOU SAVED. Oh, I'm sorry, am I shouting?

If you need unpremultiplied data - don't write it into OpenEXR with transparency, or TIFF with transparency. Instead, write the transparency/alpha channel into an unassociated alpha channel. (unfortunately, this means Photoshop can't read it from EXR right now because we only open the ARGB channels, but Photoshop will happily open up to 56 channels in TIFF).

[Chri...@adobeforums.com]

Alan - read the previous posts, please. I'm not redefining anything - I'm doing what the file format says we are supposed to do. There is no other interpretation available -- we do what we're supposed to. If Nuke has a bug, why would Adobe duplicate that bug? If Nuke fails to read the file format specification, why would we reproduce the same bug?

[Chri...@adobeforums.com]

Why are people joining the forums and making their first forum post to this topic without reading the previous posts or taking a few minutes to find out what the heck they're talking about?

If you want the Photoshop behavior with regard to the A channel in OpenEXR to change, you are going to have to take it up with the folks who write the OpenEXR spec. That spec says that the data is to be interpreted one way, and one way only -- which is exactly what Photoshop is doing. If you want the data to do something else, or mean something else: please use another file format that does what you need, or change the EXR spec.

[ja...@adobeforums.com]

Chris Cox wrote:
Even if you work with it unpremultiplied while in the application (like it always is in Photoshop) - you already premultiplied it when it went into the EXR file. YOU ALREADY LOST DATA WHEN YOU SAVED. Oh, I'm sorry, am I shouting?

Hi,
Where in the spec do you read the above, about doing multiplication of the RGB channels with the A channel as the data gets written to disk?

All I can find is; "The [channel's] name tells programs that *read* the image file how to *interpret* the data in the channel." (page 4 of TechnicalIntroduction)

I can't find the paragraph, where it says you have to multiply the RGB channels with the Alpha channel as the data is written to the EXR file, thus loosing data.

Cheers

[m._h...@adobeforums.com]

This is seemingly a dead end, in terms of working with this particular representative. Is there another Adobe representative that can weigh in on this topic?

[Chri...@adobeforums.com]

janz - read the existing posts.

m. hutch - read the existing posts. You've already burned the bridge with the one person who could or would have helped.

[sam_cu...@adobeforums.com]

These "people" you are so flippantly addressing, are industry professionals who have spent the last 2 decades or so up in the small hours of the morning writing elaborate scripts or awkwardly contorting already strained pipelines to decieve Photoshop into reluctantly relinquishing relivant images, so you can casually claim your product was used on [insert film here].

Adobe Photoshop Engineers would be wise to listen to their user base, especially when they have so patiently explained the situation. And rest assured, as gut wrenchingly painful as it is to read this mindlessly repetative thread; we have.

consider this fromt he open exr documentation ( <http://www.openexr.com/photoshop_plugin.html> )
"Un-Premultiply: by convention, OpenEXR images are "premultiplied" - the color channel values are already matted against black using the alpha channel. In Photoshop, it's more convenient to work with unmatted images. It's important to use this option rather than un-premultiplying the image within Photoshop, because the plug-in will un-premultiply before applying exposure and gamma correction.
This option will have no affect if your image does not contain an alpha channel."

by convention OPENEXR images are premultiplied, sure, by convention, you shouldnt wear white socks with sandals, but that wont stop vfx folk from doing it!

Point being, this is not an unreasonable request, it is entirely trivial to impliment, and noone has been anything but patient when requesting it.

would you kindly reconsider.
_sam

[Chri...@adobeforums.com]

No, OpenEXR files are premultiplied by definition. If you want to change the definition, talk to the OpenEXR folks. Photoshop is using the existing definition for the file format.

We do listen to users, a lot. But sometimes users make mistakes. Sometimes they ask for things that would do more harm than good. Sometimes, they even ask for things they really, really don't understand. And we try to explain, we try to help them understand (and help us understand why they're asking for something bizarre). Are you listening?

When the OpenEXR file format specification changes, we will reconsider. Until then, I strongly suggest that you use a file format more appropriate to your workflow needs.

[Alan_...@adobeforums.com]

Hi Chris,

I read all the posts before I posted. Yes, this has been cross-posted to the Nuke users list.

Strict adherence to the spec may work in the world of engineering, but we're in a business where specs evolve. The spec was designed for doing professional visual effects work. If you're going to implement the spec, it would be helpful if you learned a bit about how it is used in professional visual effects/CG production. I've seen contributions to this thread by people whose names are on the spec. They might be able to point you in the right direction.

The number one requirement that all of us have is that if a tool reads in data, the tool should be able to write it out without changing it. Clearly, this is broken for some users.

You're reinforcing a frustration that so many of us have with working with Adobe products- there's the Adobe interpretation of computer graphics, and there's an industry consensus, and they're not the same, and the ways that they are different often seem pointless.

[Chri...@adobeforums.com]

Photoshop does read EXR data in and write it out with minimal change.

Yes, specs evolve. But the EXR spec. has not changed. Again, we'll reconsider when the spec. changes. Trying to "evolve" the spec. by ignoring it just leads to trouble (and I'll offer this topic as exhibit #1).

If you try to use OpenEXR and expect un-premultiplied behavior - then it was broken the moment you wrote the data into an EXR file.
But according the the EXR spec. Photoshop is doing what it is supposed to do. If Photoshop did what you ask, it would break interoperability, and would still not do what you need (unless everyone agrees to always treat EXR as non-premultiplied all the time, and that just breaks all existing files and existing versions of applications).

No matter how many people try to use a screwdriver to drive in a nail, that doesn't make it the right tool for the job. You have other tools, that are more appropriate for the job -- use them.

[Susumu_...@adobeforums.com]

Have you seen the ILM's photoshop exr loader Chris?

You can downloaded from the openEXR site.

It let you unpremult the alpha and even gives you an option
to change the gamma and exposure.
I've been using it and I love the OPTION I have with that plugin.

The reason I wish you guys would come up something like that is that
the ILM exr plugin doesn't support 32 bit, and it's been causing
some issues in recent shows we've been working.

I assume over 95 % people who use the exr format in Photoshop are people in the VFX related, and at this point as I read this thread, pretty much 100% of the users WANT to have the option to unpremultiply the alpha.

Even if you are right about how you implemented the spec, no one is happy with it, and don't want to use it.

Then, I don't see why you would even have exr format support in photoshop. You might as well mention in the spec sheet that Photoshop supports exr but no one in the VFX industry likes it, and recommend to buy proEXR as a alternative solution.

Wouldn't you want to have a feature that makes people happy, and actually use?

[Chri...@adobeforums.com]

You seem to be confusing your segment of an industry with the larger audience of Photoshop users. People are using the EXR plugin shipped with Photoshop, in many industries. Only a few have complained. VFX represents a very small fraction of the people using the EXR file format. But Photoshop has to support everyone using the format, in many different workflows, interoperating with many other applications.

If you don't like the way EXR is designed, you are free to use another file format, or petition the EXR folks to update their spec. But we implement the current spec.

None of you have really talked about what you're trying to accomplish -- you're still asking for your imagined solution to a problem as you understand it (back the the screwdriver for nails thing). If you want a useful solution, we're going to have to talk about the larger problem, larger workflows, and consider alternative solutions (you know, reach for a hammer).

PS. Inviting drive-by postings by people unfamiliar with the issues really is not helping your case.

[Chri...@adobeforums.com]

PPS. This forum software blows when you want to format the text.

[Diogo_...@adobeforums.com]

Break interoperability with what exactly?

Because for now the interoperability you say is already broken and prevents me from bringing any EXR that went trough PS to my comp package as it was and should remain.

And even tho I do get your point regarding the specs I still can't see how something as simple as this, which could be easily solved by a really silly PS Action if it worked the other way around would do more harm than good.

The OpenEXR docs haven't been updated since 2006 and it says "By CONVENTION, all color channels are premultiplied by alpha" and not "All color channels MUST be premultiplied by alpha", so even by that time they've left room for different ways of dealing with this.

But as you said there are other tools that are more suited for the job, in this case the current Photoshop built-in EXR reader just isn't one of them.

Meanwhile if you really need OpenEXR files in Photoshop better spend 95 bucks on the ProEXR plugin from fnord or just dump Photoshop till ILM takes the time to update those three text lines on their docs to make Adobe happy about it.

[sam_cu...@adobeforums.com]

I posted this to the nuke list in the hope the people most affected by the current implementation would share their wisdom and help improve future versions of Photoshop.

These are the people that you should be turning to for guidance, its their visions that will become the commonplace features of Photoshop CS18.

This is the exact opposite of using a screwdriver to hammer a nail, the founding intention of exr was to provide a FLEXIBLE format for the VFX community who were feeling restricted by the regular formats available in 99.

I can guarantee the other industries enjoying the pleasures of exr would be equity elated to see the requested feature.

At its most basic:
A ) If an element cant pass through our studios pipeline utterly unchanged, I have failed.
B ) If an element cant pass though an image manipulation package utterly unchanged you have failed.

Saddly A is dependent on B,

And a specific practical example, um.... i have an exr with information in the A channel, i save it from photoshop, at a later date the A channel is deemed unsatisfactory, i open it again.....

[David_...@adobeforums.com]

Why does the EXR spec push premultiplication?

[dekek...@adobeforums.com]

Most of the troubles are issues with how we use exr in other applications that don't tie the rgb to the a. For example textures on a 3d model. We often times paint beyond the border of the alpha because depending the filtering a 3d app uses when it maps it onto the 3d model, you will often times get 1-2 pixels of black on the borders of the UV's. So it is very important to keep that extra data beyond the alpha.

With compositors we will get matte paintings with extra information outside the alpha which often times we will use at a later date because we are going to change the alpha inside our compositor. The current way photoshop reads and writes openexr forces us to write unpremultiplied images to bring into photoshop and then when we do have mattes for separate layers we have to write them to a separate files so photoshop doesn't nuke the information outside it.

Another big issue with the exr reader is it crops the image down to the bounding box(DOD). When I give someone a 1920x1080 image, I expect it to read into photoshop the same, not as a 1024x1024 image. The placement of objects in the frame is very important.

>You seem to be confusing your segment of an industry with the larger
>audience of Photoshop users. People are using the EXR plugin shipped
>with Photoshop, in many industries. Only a few have complained. VFX >represents
a very small fraction of the people using the EXR file >format.

Exr was made by vfx artists for vfx artists. We are the audience it was made for, not the larger audience of Photoshop users. Even though the spec doesn't specifically lay it out that way it would be nice if there was a check box so the image is read in as unpremultiplied with the alpha in the channels as a b&w alpha and not as transparency.

[Susumu_...@adobeforums.com]

I am very aware of that VFX is a small potato for Adobe.

But I was specifically talking about photoshop users who use EXR file format, and if you say there are other industy using this format more than VFX industry, could you tell me who that is?

I might be the ignorant one here if DTP or web are using EXR format
more than VFX industry, and that would be a big news for me.

At this point, I am convinced that there are nothing we could change your mind, and I am giving up to have any hope for adobe to implement anything good for VFX.

Very sad.

[Matthew_S...@adobeforums.com]

I currently work in web and I am an aspiring matte painter.

I have never used the EXR format for web design or DTP. In fact, the only time I have read, heard, or talked about EXR it has been in relation to VFX. I have never used EXR in my web design career. Most of my colleagues/friends who are amateur/pro photographers don't use EXR. The only other industries that I can think of that uses Photoshop would be medical image analysis, crime scene image analysis, and architecture. I doubt these industries use EXR on a daily basis.

Are there any other industries using EXR?

Regarding some of the messages that have been posted here. Everyone knows what's been said. There's no reason, other than to be facetious, to quote some of the remarks made. But I do feel that it's important to note that for matte painters such as Susumu Yukuhiro, Photoshop is our only option for finished matte paintings. There is no other tool besides Photoshop for compositing/painting photo-real matte paintings. Cinepaint in it's current form can't offer the functionality that a feature film matte painter requires.

I hope that the EXR documentation can be updated so that the Photoshop crew can implement updates to the way that Photoshop handles OpenEXR. However, it would be also be great if Adobe implements features that its customers ask for.

[Zap_An...@adobeforums.com]

The error here is that Chris is interpreting the word "premultiplied" literally. Many people do, incorrectly. I really hate the word, actually, because it leads you to believe it's literal meaning, that something has been multiplied with something "before" (i.e. "pre" something).

THAT IS WRONG. It is a total misrepresentation of what "premultiplied" means.

I don't know what a better word would be, but it's meaning is "dont' multiply the color-channels with alpha".

I.e. in non-premultiplied (aka "straight" alpha), a compositing operation would be

r = fg * fg.alpha + bg * (1 - fg.alpha)

And in "pre multiplied" the compositing math is

r = fg + bg * (1 - fg.alpha)

Notice the lack of a multiplicatoin on the fg? This is what lead the people to name this to say it is "pre multiplied". It isn't, really. It just means IT HAS THE PROPER RGB DATA TO BE ADDED TO THE MATTED BACKGROUND. This is *****NOT****** and I repeat * N * O * T * the same as "having already premultipled it with alpha"

Because this is a completely legal premultipled RGB color (1.0,1.0,0.0,0.0).

This is 100% transparent luminiscent yellow.

When composited properly, according to r = fg + bg * (1 - fg.alpha) it ends up ADDING yellow on top of the (unmodified) background. This is a very common workflow that renderers output such channels.

The whole idea that for a zero alpha, RGB data is always zero (or can legally be thrown away) is WRONG. It is a complete misinterpretation of the concept of "premultipled" alpha. It is a total misunderstanding, going so far as some documents claiming this "illegal" completely erroneously.

(For street cred of my position, since that seems necessary here, I had this discussion with Alvy Ray Smith, the guy who *invented* the Alpha channel, and he agrees with me on this).

/Z

[buck_f...@adobeforums.com]

Thank you Zap

[Dragos_...@adobeforums.com]

"VFX represents a very small fraction of the people using the EXR file format."

Could you read again what you have written? As one user pointed out, OpenEXR was *created* by this industry, specifically for it's use.
I do suppose that your statement is either a lie to server your argument or simply ignorance, as I'm pretty sure the VFX industry is the most important user of the OpenEXR format. But maybe I'm wrong, so enlighten us and tell us which other industries have a number of users of OpenEXR which is significantly bigger than the "very small fraction" in the VFX industry.
Nobody asks you to break anything.
Use the specs as you see fit, but offer the OPTION to your CUSTOMERS to use the software in the most useful way to do their job.
I don't care about the spec. I want an OPTION in the loader to let me ignore the alpha if I WANT TO. Because *I* know how my pipeline works, not you, neither Adobe.
I'd also like you to show an example of how this addition of this option would break the workflow of someone, who would that someone be and in what industry would he/she be involved in (supposedly with a greater number of user of OpenEXR than the VFX industry).
This is so typical of Adobe arrogance. "Screw the users, we know better and we will force them to break their workflows if it's more comfortable for us". Your users ask your for *options* to make their life easier -- or at least don't make it harder -- (again, they don't ask you to break something) and you hide behind the "spec" paper and tell them to leave you alone.

Dragos

[erik_w...@adobeforums.com]

chris,

i've read through this entire exhaustive thread now and just want to mention a point that nobody else seems to be bringing up.

I can see your position with regard to CS3+4 treating the "A" channel as transparency by default, but as you have pointed out multiple times, photoshop's EXR plugin doesn't currently support more than RGBA OpenEXRs. if we want to bundle a matte with our RGB channels that does /not/ represent the transparency of the image, the only channel we have at our disposal is that A channel. anything else currently gets thrown away on import.

the suggestion of, "finding a more appropriate format" Chris Cox, "Change in EXR open from CS2 to CS3 can this be fixed?" #80, 3 Feb 2009 7:40 pm </webx?14@@.59b70e35/79>
isn't particularly helpful or realistic. visual effects facilities have entire pipelines built around specific image formats and re-structuring those pipelines around an inflexibility in a piece of software that likely makes up a very small corner of that pipeline just isn't going to happen.

the plea here is to (until the day when full multi-channel EXR support makes its way into photoshop) give your VFX user base some options with regard to how that precious "A" is handled. fine, let the default be the "right" way to interpret the data, but don't cut us off at the knees. being flexible is of primary importance in production.

regards,
erik winquist

btw..

"I probably do more compositing before lunch than you will do all year."Chris
Cox, "Change in EXR open from CS2 to CS3 can this be fixed?" #62, 3 Feb
2009 12:04 pm </webx?14@@.59b70e35/61>

give me an effing break.

[Brendan...@adobeforums.com]

Wow, this thread is pretty intense. I wish someone had pointed me to it earlier. I'm a bit biased, but I agree that ProEXR solves all the alpha problems mentioned here. It was created by someone who works in the VFX industry (me). You can try it free for 15 days.

This is covered in the ProEXR manual and in this thread, but to recap: OpenEXR files use premultiplied images, while Photoshop long ago chose to use straight. Turns out this was an unfortunate choice because, as Florian and others pointed out, any non-black premultiplied pixels with a black alpha will get decimated when converted to straight. Nuke, Shake, and Fusion are premultiplied, so they don't have this problem. I can't think of any advantage to using straight, but it would probably be hard to switch back at this point.

Sometimes VFX artists don't actually want Alpha to be transparency, although that is the standard thing to do and it's the ProEXR default as well. But we also give you a dialog for changing the behavior if you like. You can keep the alpha channel separate and choose whether to un-multiply the RGB. I don't know if Adobe should change what they're doing in their own plug-in, but I'm glad I could swoop in as a third party developer.

If you have other ideas for making ProEXR better work in a film workflow, let me know.

Brendan

[Christop...@adobeforums.com]

[QUOTE] You seem to be confusing your segment of an industry with the larger audience of Photoshop users. People are using the EXR plugin shipped with Photoshop, in many industries. Only a few have complained. VFX represents a very small fraction of the people using the EXR file format. But Photoshop has to support everyone using the format, in many different workflows, interoperating with many other applications. [/QUOTE]

Chris, we've been over this before on the CS4 beta forums and it really surprises me how you stick so much to the "EXR File Specs"

Obviously a lot of people are really annoyed that they can't use EXR (a file format created BY the FX industry FOR the VFX industry!) anymore like they did in CS2. First I thought it was just Mental Ray's Problem, but it turns out that Renderman creates the same problems.

I really think it is Adobe's time to move on this and make a little File Open dialog where you can choose how to treat Transparency and Alpha channels.

It doesn't matter if it's different from the EXR specs Chris!
People need to be able to use their renders and pipelines and need this flexibility!

We also use ProEXR sometimes, but it is really sloooooow, so at the moment we have a separate machine with CS2 installed and save all our EXRs as PSB files, which is very annoying too.

Best Regards - Christoph C-:

[Thomas...@adobeforums.com]

Chris Cox:

- Either make it an option in preferences ("Treat additional channels as transparency or leave them alone")

- Or apply the Alpha as a layer mask, so the user has the option to enable or disable it at will.

The current implementation is destructive and very very very annoying.

And this is true for EVERY single format that supports more than RGB, not only EXR.

I do graphics for 15 years and I NEVER EVER even once wanted the behaviour that Photoshop is showing.

Photoshop it THE melting pot for billions of images from thousands and thousands of sources.
This is not about being right or SPECs etc. (you can't win this uphill battle anyway)...
This is about creativity software.
People want a choice.

Cheers,

Thomas Helzle

[Alan_...@adobeforums.com]

Hi Chris-

This is not a game where you score points by belittling the work of your customers.

The folks who have commented on this thread as a result of cross-posting in the nuke list are not a bunch of drive-by hecklers, and we seem to be doing our best to add some clarity and represent our interests.

The computer graphics and visual effects community does have a sense of ownership over OpenEXR, because it was designed to work well in our pipelines. Adobe's customer base is so large that a seemingly miniscule change like we're talking about can break the things that we depend on. TIFF is a good example of this.

The EXR spec hasn't been updated for a while- probably because the folks who wrote it have moved on to other problems. Perhaps if you're not interested in listening to the concerns of the community, you could simply not support it, and give some breathing room to the plugin developers.