What is the Best ?

[Star QualityVideo]

Hi, what is the best workflow for blending ND15 filter photos with the other photos for the  HDRI panoramas?  When I try it the blends are hard edges and black rings are in the center of the sun.

I am shooting 5 photos 3ev 0-+-+.  I then add the ND filter and shoot the same set.  I add the photos in PTGUI and link them manually following the instructions on this board, but always fail.

[Erik Krause]

Am 02.09.2023 um 06:20 schrieb 'Star QualityVideo' via PTGui Support:

> Hi, what is the best workflow for blending ND15 filter photos with the
> other photos for the HDRI panoramas? When I try it the blends are hard
> edges and black rings are in the center of the sun.

The images taken with the ND filter have the same exposure metadata as
the images without the filter. Have you taken this into account?

You can compensate for that, adjusting f.e. the ISO value on Image
Parameters tab. Then the correct value should show up in the EV column.
Does this help? If not, please make a complete bracketed set of images
available for download. Half size jpeg copies would be good.

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

[PTGui Support]

For your 15 stop ND filter, the equivalent ISO factor is 2^15 = 32768.
So you could set ISO to 1 for the ND filter images and ISO to 32768 for
the regular images.

You can do this in the Image Parameters tab. Multiple cells can be
selected and edited in one go.

It will only work well if your ND filter has no color cast, this is not
always the case from what I've seen.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

[Star QualityVideo]

Ty! That works well.  However, when I get to the stage to Align images the option to merge images to HDR does not work.  It undoes the 10 images ND filter set and creates two sets out of it.  Is there a way to override that? 

[Star QualityVideo]

I can regroup the ND filter set after alignment but the final HDRI is very dark when I add the ND filter set back to the group.  I try to upload it.  TY.

[Erik Krause]

Am 03.09.2023 um 02:47 schrieb 'Star QualityVideo' via PTGui Support:

> However, when I get to the stage to Align images the
> option to merge images to HDR does not work.

Do Align Images before you set the ISO values. After that, do Optimize
(F5) only. Align Images initializes many values and is only intended for
use immediately after loading the images.

[Star QualityVideo]

Thank you very much.  I am getting so close...

In this thread, it states the opposite workflow: https://groups.google.com/g/ptgui/c/b1UZRFkM60U/m/IJ6YNHAWAgAJ

Here si the quote, " In that case the exposure sequence is irregular, PTGui cannot link the
images for you automatically so you need to do this manually:

- Load your images, but don't link the HDR exposures yet
- Click Advanced
- Go to Lens Settings
- Adjust the ISO column such that your ND images have ISO 1, and your
other images have ISO 1024. You can set multiple values at once by
selecting a range of cells and entering a value

- Go to Source Images tab
- Select a series of bracketed images belonging together (for the sun
frame this should include both the images with and without ND filter)
- Right click, 'Link Selected Images'
- Repeat until all bracketed sets are linked
- Go to Exposure/HDR and choose Precision: Float (see the tooltip for
more information)

Finally, run Align Images and proceed like any other HDR panorama.

Kind regards,

Joost Nieuwenhuijse"

Here Align is the last thing done.

[Erik Krause]

Am 03.09.2023 um 20:55 schrieb 'Star QualityVideo' via PTGui Support:
> In this thread, it states the opposite
> workflow:https://groups.google.com/g/ptgui/c/b1UZRFkM60U/m/IJ6YNHAWAgAJ

Yes, I was wrong, sorry. I should have tested before writing. So I don't
know what's going wrong. Please make a complete bracketed set of images
and the project file available for download. Half size jpeg copies would
be good. Use wetransfer, dropbox or similar.

[Star QualityVideo]

Essentially my Nd set looks like this (see attachment) when the exposure value is set low afterwards when checking the image quality.  It should look smooth and blend well.

I will upload soon. TY very much.

[Star QualityVideo]

Here is a link to the images.  TY

https://www.dropbox.com/scl/fo/dlknszcenir34msh8vcjo/h?rlkey=0vyn53tugokjochszahzm3n9u&dl=0

[Erik Krause]

Am 04.09.2023 um 00:27 schrieb 'Star QualityVideo' via PTGui Support:

> Here is a link to the images. TY

I played a bit with your images, but got no very good result. I Loaded
all images in PTGui, agreed to link bracketed images and passed Align
Images. Alignment was good except the ND filter images. I then set ISO
32768 for all but the ND ones, which got ISO 1. Then I dragged the ND
group on Image 1 to have it share the alignment.

There was a distinct border between the ND group and the rest around the
sun. This has three reasons:
1. In the darkest non-ND image there is a horizontal streak right and
left of the sun, which isn't present in the ND images. Since this streak
is brighter than the sun star, which causes a visible border.
2. The ND filter density is not 15, it's most likely 16. I tried to
manually set ISO values, such that the border visibility minimizes and
reached that at ISO 64000, which is roughly 2^16. The border at the
streak is still visible, though.
3. The ND filter has a slight purple tint. This should be corrected
during raw development. PTGui can't do that.

(Project file attached)

> I can regroup the ND filter set after alignment but the final HDRI is very
> dark when I add the ND filter set back to the group.

That's quite normal, if you output an HDR format. PTGui scales the
output such that 1.0 corresponds to white in the middle exposure of your
bracketed sets. As it is a floating point format, there is still no
clipping whatsoever.

May I ask what your goal is? Do you shoot for image based lighting? If
not, using that many brackets is superfluous. If yes, it might be better
to not use a ND filter either, but more standard brackets instead. You
can do composite bracketing by f.e. also changing ISO and aperture. Or
even simpler: Since only the sun exceeds the dynamic range of the non-ND
shots, paint the sun with the desired brightness in your image editor.

BTW.: The sensor of your camera already captures more than 14 EV. With
bracketing 12 EV you get a total of 26 EV dynamic range, which should be
enough for all HDR needs. Not even the Spherocam HDR (used for a lot of
Hollywood productions) has more...

[Star QualityVideo]

Thanks a billion.  Your dedication is inspiring.  As to what is the Best...?  You are my friend.

I am shooting for image-based lighting to be used in 3d apps like Blender.

You have given me some great leads for improving my workflow. I will get to work. Let the fun begin!