Photo unable to render more than 8 bit color depth in RGB/16 documents on display

[NotMyFault]

Hi,

this has maybe been reported before, I can't find the old post right now.

If you have a display capable to display 10 bit (or 12 bit), you clearly want to use this in Photo.

Unfortunately, while being capable to crate such documents correctly, the rendering to the display is always limited to 8 bit color depth.

Only when you switch to RBG/32 and EDR mode, Photo is able to render more than 8 bit color depth to the display.

 

The screenshots (from M1 Mac mini with 10 bit capable display) shows the issue by comparing Mac Preview and Photo showing the identical test image.Test file:

https://raw.githubusercontent.com/jursonovicst/gradient/master/test_sequences/1920x1080/gradient_1920-1080_25-50.png

[NotMyFault]

please find a even more convincing example below.

I made 3 copies of the file in RBG 8 / 16 / 32 bit.

Then, I exported a PNG version directly from photo. 

Note that the 32 bit version exports to a 16 bit PNG, but it uses a linear gamma, so the grey color differs fro the other examples.

Then again, I opened the PNG files in parallel to the 3 afphoto files and made a screenshot:

Imported this screenshot again into Photo, added a curves adjustment to boost the contrast around the visible mid-grey tone.

Now you can clearly see that Preview renders 16 bit PNG with all 10-bit color depth, whereas Photo only renders 8-bit color depth.

 

grad rgb 8a.afphoto grad rgb 16a.afphoto grad rgb 32a.afphoto

[NotMyFault]

To answer some possible questions:

• Preferences->Dither gradients has no impact. The gradient was created by a procedural texture filter, not by a gradient fill.
• I strongly assume this impacts all platforms (Windows, MacOS, iPad OS)
• this never worked in any Version of Photo since about 1.5. I use 10bit capable displays since 2009, and a 16bit capable Scanner since 2003. it is a real pity that Affinity does not allow to utilise this essential functionality. Going to RGB/32 is no suitable workaround, because of 2x storage, linear gamma issues, unavailability of many live filters.
• Will try again with HW acceleration inactive.

[Lisbon]

This question probably wont make any sense but here goes.

Isn't the 8 bit preview intentional in order to improve the system performance?

If im not mistaken even photoshop is limited to 8 bit previews. Only recently, they added an option to improve previews in 16-bit documents.

[NotMyFault]

1 hour ago, Lisbon said:

This question probably wont make any sense but here goes.

Isn't the 8 bit preview intentional in order to improve the system performance?

If im not mistaken even photoshop is limited to 8 bit previews. Only recently, they added an option to improve previews in 16-bit documents.

Well - My old PC (2018)  and current M1 Mac are perfectly capable to render RGB/32 documents in Photo with higher bit depth, and ok performance

I don't need an App which renders a document fast but wrong. I need an App which renders the document correct, in best possible performance.

 

I always hated disliked jpeg images for visible banding in smooth blue sky caused by the 8 bit limit. Unfortunately Apple still creates 8-bit only in HEIF, whereas Canon / Sony create files with more bit depth. And I hate dislike Affinity to enforce dithering on those self-limited 8 bit gradients (even in RGB/16 documents.

[NotMyFault]

Bump - any comments from mods?

[NathanC]

Hi @NotMyFault,

This has not been forgotten about and i've been able to replicate this behaviour with 16 bit images, i've raised this internally and will come back to you when I have a definitive answer as to what's going on. 🙂

[NathanC]

Hi @NotMyFault,

Going back to the original gradient image I've been able to see a clear difference between the 8 and 10 bit gradients with the addition of a curves adjustment on a 10 bit display within APhoto, as there are four bars for every one. If you open the attached file on your side is this the same for you?

I'm still looking at why this isn't the case with your sample files, perhaps it is related to the procedural texture.

Gradient Test.afphoto

[NotMyFault]

2 hours ago, NathanC said:

Going back to the original gradient image I've been able to see a clear difference between the 8 and 10 bit gradients with the addition of a curves adjustment on a 10 bit display within APhoto, as there are four bars for every one. If you open the attached file on your side is this the same for you?

Thanks for following up. adding a curves adjustment on the original file does not prove the presence of 10 bit rendering. it will shift the color values so that you can even spot the difference on a display with only 8 bit color depth. To proof this: simply add a posterize adjustment with 256 colors. It will show almost the same result. Increasing to 512 or 1024 will not render different to 256.
 

Only if applied to a screenshot of the file rendered in Photo, the levels adjustment would be a valid tool to verify the actual display bit depth.
 

[NathanC]

Hi @NotMyFault,

Thanks for clarifying, since i've been able to replicate this with your second set of example images i've consulted with QA, collated this and logged it with the developers.

[NotMyFault]

bump. still not fixed in V2.2.

[Bit Disappointed]

😞

[NotMyFault]

Another new case