Strange blending colours when stitching Canon 5D2 raw files for gigapixel image

[Nitroman]

Hi !

I'm just experimenting with stitching multi row gigapixel images using
my Canon 5D2, Nodal Ninja 5 and 200mm lens - but have found a problem.

The final image shows strange colours and contrast when using the raw
files. They look like blending errors. It only happens if i import the
raw files - if i convert the raw files to jpgs first it;'s not a
problem.

Any idea what the problem is ?

I can upload pics but not quite sure where i can do this on the Google
Group PTgui Support Forum.

Please help !!

Many thanks ...

[Erik Krause]

Am 11.05.2012 09:40, schrieb Nitroman:
> The final image shows strange colours and contrast when using the raw
> files. They look like blending errors. It only happens if i import the
> raw files - if i convert the raw files to jpgs first it;'s not a
> problem.
>
> Any idea what the problem is ?

The problem is dcraw, which is used by PTGui to convert raw files. The
easiest solution is not use raw directly but use a decent raw converter
which delivers far better quality anyway, at least if you convert to 16
bit TIFF.

However, here Canon 5D2 raws look fine in PTGui. My dcraw version is
9.11 from January 16 this year. You can find it in the dcraw subfolder
under PTGui program folder.

> I can upload pics but not quite sure where i can do this on the Google
> Group PTgui Support Forum.

Use http://ge.tt or similar service...


--
Erik Krause
http://www.erik-krause.de

[Nitroman]

Thankyou Eric. Appreciate your advice.

I'll look in to shooting more raw tests and then try Adobe Camera Raw
converter to make some tifs.

Shame PTgui can't convert the raw files better as it lessens the work
flow.

Best wishes ... Nitroman :)

[Erik Krause]

Am 11.05.2012 17:16, schrieb Nitroman:

> Shame PTgui can't convert the raw files better as it lessens the work
> flow.

Raw conversion is an art in itself, where many man-years go into
development. It's better to leave this for a dedicated program.

And no, it would not lessen the workflow, since you would spend exactly
the same amount of time adjusting the raw conversion parameters as you
would do in a separate raw converter. In fact it is faster, since you
always can set up a raw converter to batch convert all images you shot
unattended.

I ever was against PTGui importing raw files directly because I expected
exactly that - people demanding more than very basic support which might
detract Joost from implementing far more important features.

[Joergen Geerds]

On Friday, May 11, 2012 11:16:06 AM UTC-4, Nitroman wrote:

I'll look in to shooting more raw tests and then try Adobe Camera Raw
converter to make some tifs. 

quite honestly, if making tiffs with ACR is too much for you, why not stick to camera-internal JPGs? the quality should be good enough for you.

 

Shame PTgui can't convert the raw files better as it lessens the work flow.

I am with Erik, I never thought it was a good idea to have RAW import within ptgui, specifically for users with your attitude. Joost is doing a fantastic job with PTgui, and bad-mouthing him just because you have troubles getting your (workflow) ducks in a row, isn't fair to him. you should think about how many people are employed at Adobe to make ACR (one of the best RAW converters we currently have), and then compare their effort to how much resources David Coffin has to spare to make dcraw.

I know Joost really likes to have the ability of rudimentary RAW support in ptgui, but this is one of the moment where I personally wish it would have never happened.

</grumpyrant>

[Nitroman]

Thanks again Erik for your courteous reply. It's good to see there are
some friendly and helpful people on this forum.

I think you must have got out out bed the wrong side Joergen, unless
you always have such an abrasive and defensive attitude.

I'm incredibly grateful to all the people who are involved with PTgui.
It's a most excellent product and far better than anything else on the
market.

Nitroman

[Erik Krause]

Am 12.05.2012 07:54, schrieb Nitroman:
> I think you must have got out out bed the wrong side Joergen, unless
> you always have such an abrasive and defensive attitude.

You should neither blame Joergen, which is one of the most helpful
persons on this list nor Joost, who was talked into adding raw support
to PTGui. Does your car brew beer? If so, would you expect it to be a
Budweiser?

[Nitroman]

I'm grateful for all advice anyone is kind enough to give.

Raw support is an incredibly helpful feature when i'm producing hdr
domes for car companies. I for one am glad Joost has included it
within PTgui. Once again ... thank you for what i believe is the best
product on the market.

Sadly my car doesn't brew beer Erik ... but i'd like it to ! :D

If it did ... i'd be the first to offer you all a pint. :)

[Erik Krause]

Am 12.05.2012 19:47, schrieb Nitroman:
> Raw support is an incredibly helpful feature when i'm producing hdr
> domes for car companies.

Did you ever try to simply shoot jpeg and compare the results? I think
you would be much faster and the quality would be the same, especially
if you do HDR...

[Ken Warner]

I never use PTGui's raw converter. I also feel that while it was a most requested feature, it is better done with other tools. Even UFRaw gives you more control and it uses the same dcraw converter.

And jpegs out of most cameras are really good. Probaby much better than you can get with dcraw.

[Erik Krause]

Am 12.05.2012 21:20, schrieb Ken Warner:
> Even UFRaw gives you more control and it uses the same dcraw converter.

dcraw are two different thing. A collection of decoding algorithms and a
rudimentary image output - all together in a single command line
program. The biggest achievement of dave coffin is having reverse
engineered a gazillion of raw file formats, some of them encrypted.
Without that there where no UFRaw, no RawTherapee and even no ACR - at
least not in the form it is now. We must be very grateful for the effort
he puts in dcraw since without it raw conversion of outdated formats,
where the original producer doesn't provide software anymore, would be
very difficult or impossible.

But reading raw files alone is no raw conversion. To form and output an
image some more steps are necessary. One big part is interpolation. In
RawTherapee f.e. you can choose between different algorithms and you can
see that the better are computational expensive. They take much longer
than the simple ones and they give visually better results. dcraw can
use three different interpolations, each of which has different problems.

Other part is highlight restoration. If you ever looked at unprocessed
raw data (yes, dcraw can output that), you'd notice that highlights
aren't uniformly clipped to maximum value. Each color channel has a
different clipping value, and even that is not uniform across an
overexposed area. If you push dcraw dynamic range to the max you often
get colored areas f.e. in originally grey clouds. To avoid this, dynamic
range must be reduced, which is what PTGui does when it calls dcraw.

So the image output part of dcraw is less more than a proof of concept.
Most raw converters which use dcraw as a basis only use the file
decoding part and implement better algorithms for the rest. These
algorithms need to be very sophisticated to compete with the established
programs.

Please have a look at the dcraw manual to get an idea how complicated
raw conversion actually is:
http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html

[Ken Warner]

Yes, I understand all that. And you've summarized the issue well. So it's expecting a lot for PTGui to also offer more than the default conversion of raw files. I think that's both our points.