HDR exported picture is burnt

[cristian5th]

Hello.

I'm running Affinity Photo 1.11.6 on MacOS Ventura 13.4.1.

After creating an HDR picture in Affinity and being happy with the results displayed at the screen, the exported image has burnt areas all around. It does not correspond to the displayed image in Affinity Photo. This has proven to be independent on the export format (jpeg, tiff,...) and the issue is repeating on every HDR processed.

Further investigation shows that, even a screen capture of Affinity Photo's window is also burning the image. I had to take a picture of my screen to be able to show the display difference. You can see how all is burnt in the attached screenshot.

[NotMyFault]

If you create HDR images, e.g. by HDR stack from exposure bracketed files, these documents are in RGB/32 format, with unbound color values which exceed what can be stored in jpg or tiff files.

You need to export either to a format supporting hdr images like EXR or HDR, or use tone map persona to reduce the dynamic range and color values so it can be exported to jpeg.

Please include the document format into the screenshot (window title when hand tool is active), and the 32-bit preview and histogram expanded. If the file has lightness above 1.0 in histogram, those values will be clipped when exporting to jpg (as you observed).

I made hundreds of hdr images with Photo V1, and it works great in most cases. 
 

When I remember it right, Affinity v1 has some Limitation wrt to tiff and 32 bit format. 

[cristian5th]

Hi, NotMyFault.

Thank you for your explanations. I am aware of the higher dynamic range that is not to be saved in a jpeg, but as you mention, the tone mapping is compressing the range, and therefore allowing to save the image in a jpeg. That is were I'm getting confused, because the problem that I mention is after tone mapping.

Find enclosed some captures of the export preview where, even in 32bit exports, the image is still burnt. This is absolutely not what I'm seing in the screen before exporting.

I have been playing around with all the options, trying to understand this issue, and I have stumbled on the "Clamp to SDR" checkbox within the tone map persona. When I activate this checkbox, then I see the image burnt also in the screen and not only when I export. Maybe this checkbox has some usage?

Anyway, why after tone mapping I'm still having lightness values above 1? This shouldn't be, should it?

[NotMyFault]

Tone Mapping Persona does not reduce lightness above 1. Instead, it has 2 main functions:

• global compression: compress color values between 0 and 1, making dark areas brighter and vice versa
• adding local contrast / improving local contrast 

You need to reduce excess lightness before entering tone map persona, e.g. by curves, lightness, expose adjustments.

1 hour ago, cristian5th said:

"Clamp to SDR" checkbox within the tone map persona. When I activate this checkbox, then I see the image burnt also in the screen and not only when I export. Maybe this checkbox has some usage?

yes, it shows areas which get clipped (clamped) when exported / converted to non-HDR formats. But it will not produce a good image.

Below you find a PT filter which shows any pixels with excess brightness, and renders the rest transparent. It servers the same purpose.

So the normal workflow to export HDR images to jpeg is:

1. create HDR image 
2. reduce brightness to range 0..1 (curves, lightness, etc). This will darken the image
3. use tone map to boost darker areas, and re-gain a usable overall brightness 
4. export as jpeg

[NotMyFault]

The 32-bit preview panel gives additional help:

It will show the maximum EV values in the image, and when you activate "show EDR clipping", it marks areas which exceed the brightness limits of the display.

[cristian5th]

Thank you for all this information. These were details that I was not aware of.

So, I have managed to display the 32-bit preview and it says Extended Dynamic Range (max 2.00, +1.00 EV). This is before the tone mapping. I understand then that I should work with the image as is, in order to reduce the max to 1.00 before sending it to the tone mapping persona. Regretfully, I don't see this number change, no matter how I lower the image lights. I applied brightness, exposure and highlights adjustment to the point to render the image totally black. What am I doing wrong?

I enclose the Afphoto image for playing.

Thank you.

Triglav.afphoto

[NotMyFault]

One additional step is required just before starting tone map persona:

either „merge down“ the exposure adjustment, or „merge visible“ to get a pixel layer having the reduced lightness „baked in“. 

The brightness adjustment is not suitable as it ignores values exceeding 1.0.

Exposure, curves or levels are best suitable.

shadows and highlights could worsen the image in this specific case.