Export after HDR merge blows out highlights (maybe colour profile issue?)

[Laurens]

Hi all,

I'm new to the forum and have been using AP enthusiastically for a few years. I love the HDR and tone mapping functions, but discovered an issue when exporting the document. Colour rendering clearly is not equal in the document and the exported file. I have read several issues that address something similar, but was unable to find how those issues relate to this one and what I should do.

This screen pic shows the problem in the highlights:

 

Interestingly, when I take a screenshot, the document and export are identical.

I use:

MacBook Pro 13" 2017

sRGB IEC 61966-2.1 colour profile in-camera (JPG, not RAW) and in the export settings

 

I am a nitwit on colour profiles, but it seems clear that my laptop is interpreting the document differently from the JPG+screenshot and that it has nothing to do with the screen or calibration.

 

What can I try to make these images match?

[walt.farrell]

Welcome to the Serif Affinity forums.

What output format have you chosen for your export?

[Laurens]

Thanks for the quick reply!

Here are the settings:

I tried fiddling with Resample, ICC profile (just 2 or 3 options) and Embed ICC profile - but no luck. All outputs look identical.

 

Clarification of my original comment: when taking a screenshot, both the document and export look identical with the blown-out highlights.

[walt.farrell]

JPG supports only 8 bits per channel, but HDR is usually 32 bits per channel, I believe. What format is your file in Affinity Photo? RGB-32 or RGB-8?

[Laurens]

We must be on to something! I used Document->Convert Format/ICC profile and found that it is indeed RGB-32:

After conversion to RGB-8, all detail is gone and the highlights are blown.

 

The original files are 3 exposure-bracketed JPGs. The darkest has all the details in the clouds that I wish to preserve. Do you have a suggestion how to use the HDR merge function without this loss?

As a test, I imported 1 picture (the darkest one) in HDR merge, applied a bit of local contrast, converted from RGB-32 to RGB-8 and again saw some loss of detail.

 

[James Ritson]

Hi @Laurens, if you show the 32-bit Preview Panel (View>Studio>32-bit Preview), is Enable EDR checked?

If so, this will use your display's extended brightness range to display HDR colour values (i.e. outside the range of 0-1). Whilst this is a really nice feature, you currently can't export to any kind of HDR format outside of OpenEXR/Radiance HDR, so you would instead need to work in SDR and tone map the HDR values down to that range.

The reason your images look different, I suspect, is because you're able to see values >1 on your display, but when you export to a bounded format such as JPEG, those values are simply clipped at 1.

To solve this problem, start by disabling Enable EDR, then use the tone mapping persona or a set of tone mapping macros to bring those brightness values to within SDR range. Once you have done the tone mapping, do any further edits as usual, then try exporting—you should find that the exported image now looks the same as the working copy in Photo.

In Preferences>Colour, you will find a checkbox called "Enable EDR by default in 32bit RGB views". Unchecking this will prevent the issue from reoccurring in the future.

Hope that helps!

[ColmR]

I had this exact same problem. Thank you James. It's resolved the problem completely.