Lossy DNG colour distortion

[ptodd]

I'm somewhat tempted to convert the bulk of my photo library to lossy DNG, but have noticed that Affinity seems to have some bugs with colour in this format.

For example, I tested an underexposed photo of some trees at sunset, and while Affinity renders the lossless DNG colour correctly, the lossy version is very magenta (in a way that cannot be corrected with white-balance adjustment in the develop module).

This isn't a good photo, just one that I happened to try that illustrates the problem. Both of these images are developed in Affinity with 60% shadows boost and no other adjustments.

I generally use LR for the asset-management side of things, but am holding out for an Affinity DAM (and anyway, would rather not have data in a form that only works well in certain apps). I'm sure the same is true for many here.

I don't quite know why Adobe didn't make some other choice than 8bit JPEG compression for the lossy DNG format when technology is available that ought to be able to make smaller and better quality files, but it seems that it should be adequate for many uses... indeed a poor-quality underexposed photo like this renders similarly well in either format when processed in LR, so I'd be fairly happy converting the bulk of my photos as long as I felt confident that I could still open them in Affinity.

Tested with Affinity Photo 1.10.5 on macOS 12.3.1 FWIW. Lossy and lossless DNGs are attached.

P1035400-2.dng P1035400.dng

[ptodd]

p.s. it seems like there's some geometric difference between the two output images here as well... interesting... I certainly didn't knowingly apply any lens correction / cropping / anything else.

[stokerg]

Hi @ptodd,

We do have a few issues that are similar to this logged with the Dev team but i do think this is different, so will log it separately once i've reviewed the other issues just to be sure this is different.  For now, in Affinity if you open the problem DNG file and while in Develop click View>Assistant Manager and change the RAW engine from Serif LABS to Apple (Core image RAW) then close the Assistant Manager, close the DNG files and reopen it.  It should now display correctly  

[ptodd]

2 minutes ago, stokerg said:

Hi @ptodd,

We do have a few issues that are similar to this logged with the Dev team but i do think this is different, so will log it separately once i've reviewed the other issues just to be sure this is different.  For now, in Affinity if you open the problem DNG file and while in Develop click View>Assistant Manager and change the RAW engine from Serif LABS to Apple (Core image RAW) then close the Assistant Manager, close the DNG files and reopen it.  It should now display correctly  

Thanks, I'd seen similar advice about switching RAW engine on another thread, but then lost track of it and couldn't find the option (I was looking in preferences).

The result when using Core Image RAW is better, but has problems of its own (as well as presumably not being available on Windows, which I do also use but am not necessarily massively concerned about here). In this image (same settings as before, but Core Image in AP), it seems to be bringing a lot of inappropriate green into the shadow regions:

That's (presumably) no fault of Affinity, but it does weigh against this format being viable for the time-being. I'd say that it's still bad enough to be considered 'incorrect'.

While I'm here, here's the lossy version processed by LR (I've not gone to great lengths to make them exactly match, but pretty much left on neutral defaults apart from shadow boost):

[Ron P.]

In AP, the Assistant Manager, do you have Exposure Bias & Tone Curve enabled? Try disabling those, and see if will allow you to get closer to your LR processing.

I also use LR, (the last perpetual version), and if I develop in LR, I will not use the Develop Persona in Affinity. For extreme cases, like your underexposed image, I find LR does a better job.