Problems with BLUE LEDs in RAW files

[Bit Disappointed]

In Photoshop the camera profile "Adobe Standard" shows exactly what you want while the camera profile "Camera standard" looks like what you see in Photo. It seems that the camera color profile emulations are drifting a bit away from accuracy, towards creativity.

If I choose Adobe Standard, it looks nicely blue. Capture One Professional and DxO Photolab 6 display the color beautifully blue. I highly recommend DxO, fair price, excellent rendering and camera support.

Color profiles and color spaces are the heavy and time-consuming part of the theory in photography, another good reason to take black-and-white pictures occasionally for a break, and to focus on composition.

Anyway. You get what you pay for. Adobes own profile saved me a few times in Photoshop.

Adobe's Camera Raw color profiles serve several key purposes:

Color Accuracy: These profiles are designed to provide accurate color reproduction based on the specific characteristics of various camera models. Each camera sensor interprets colors differently, and these profiles help standardize and correct colors to ensure they are as true to life as possible.

Consistent Look Across Different Cameras: If you are using multiple camera models, these profiles help in maintaining a consistent look and feel in terms of color rendition across all your images. This is particularly important for professional photographers who may use different types of cameras but want a uniform style in their work.

[calebcudjoe]

1 hour ago, Bit Disappointed said:

In Photoshop the camera profile "Adobe Standard" shows exactly what you want while the camera profile "Camera standard" looks like what you see in Photo. It seems that the camera color profile emulations are drifting a bit away from accuracy, towards creativity.

If I choose Adobe Standard, it looks nicely blue. Capture One Professional and DxO Photolab 6 display the color beautifully blue. I highly recommend DxO, fair price, excellent rendering and camera support.

Color profiles and color spaces are the heavy and time-consuming part of the theory in photography, another good reason to take black-and-white pictures occasionally for a break, and to focus on composition.

Anyway. You get what you pay for. Adobes own profile saved me a few times in Photoshop.

Adobe's Camera Raw color profiles serve several key purposes:

Color Accuracy: These profiles are designed to provide accurate color reproduction based on the specific characteristics of various camera models. Each camera sensor interprets colors differently, and these profiles help standardize and correct colors to ensure they are as true to life as possible.

Consistent Look Across Different Cameras: If you are using multiple camera models, these profiles help in maintaining a consistent look and feel in terms of color rendition across all your images. This is particularly important for professional photographers who may use different types of cameras but want a uniform style in their work.

Happy for photoshop, capture one and dxo users. For those needing help figuring it out in AP though, the information I and other provided for solving in it in AP might prove useful. 

[Bit Disappointed]

Yes, it might. But one should consider, if one is more than a hobbyist and needs to process many RAW images, whether one should not run Photo on a Mac, where Photo offers to use Apple RAW as a converter. That was the 'hidden' point in my post, you can't work seriously having to go through and remember all sorts of workarounds. And most customers won't see them, probably only 1-2% of Serif's customers are here. 

[Ldina]

@calebcudjoe Caleb, I decided to run a few more tests this morning, again using my espresso machine with the blue/cyan LEDs. I suspected that overexposure of the blue/cyan LED lights might be a big part of the problem.

I took some natural light photos of my espresso machine with my Canon 5Dmk2 in semi darkness (at ISO 3200). I took 3 exposures, one normal, one at -1 EV, and one at -2 EV. I suspected some of the magenta problem was due to clipped channels and perhaps sensor blooming as well.

It's interesting to note that the LCD preview screen on the back of my Canon 5Dmk2 camera also shows some magenta cast in the blue LEDs in all three of these captures, so even Canon's own internal processor algorithm results in some magenta cast. I shot RAW, but cameras generate JPGs internally for the camera LCD preview.

I took the darkest RAW exposure (2 stops underexposed) and edited it in the Develop Persona as a 32 bit file to help recover some of those dark shadows. Even at 2 stops underexposure, the blue channel is still clipped (255 in the B-channel). Even if I lower the highlight slider to -100, some of that magenta/purple cast dissipates, but not all. Even then, the blue channel is still largely clipped. I think most of this problem is a sensor capture issue. Once I was in the Photo Persona, a Selective Color Adjustment of the Magenta Channel corrected the problem entirely.

So, some (perhaps all?) of this magenta cast, at least in the photos of my espresso machine, are due to blue channel clipping, and probably some sensor blooming as well. Another likely contributor is the ICC Specification itself. It's a well known fact that blues often shift toward magenta/purple with brightness/saturation because the ICC spec is not perceptually uniform (at least with ICC v 2). It's well documented on the internet. I had to deal with this all the time at my last job as Marketing Director because one of our corporate colors was a bright, saturated blue. My boss "hated" purple and so I always had to compensate so our press-printed brochures and flyers didn't look 'purple' to his eyes. That was partly due to the ICC Spec and also the inability of CMYK inks to reproduce those bright, saturated blues. (He was too cheap to pay extra for spot colors.)

"Highlight recovery" often involves various algorithms that try rebuild the data in clipped channel(s) based on whatever data is available in the remaining UNclipped channels. These are educated guesses because those clipped channels have no data, so the software cannot know for certain how to interpret them or what color the original was. LightRoom and Adobe Camera RAW use this approach, and probably others. Different algorithms and different profiles result in different guesses. OEMs know their sensors, cameras and lenses the best, so they probably have the ability to do a better job than most 3rd party vendors in recreating the actual colors (or should).

The above highlights why I was a bit hesitant to upload my original files as an example. I was concerned that channel clipping (especially in the blue channel) was a big contributor to the magenta/purple cast in what my eyes saw as blue or cyan. 

[Ldina]

Attached is the 32 bit, full sized afphoto file discussed in my previous post, with the embedded DNG. This DNG RAW file was intentionally underexposed to help me investigate whether channel clipping was a big part of the issue. It is. The AfPhoto file is HUGE as it is a full sized 32 bit file with additional layers (AP v2.4.0).

I've also included a small JPG export (sRGB) from the 32 bit file for those who aren't interested in downloading the above behemoth. This is fairly accurate to what my eyes see, but the sRGB color space loses some brilliance in those bright blues and cyans.. 

20240303-IMG_7067.afphoto

[calebcudjoe]

7 hours ago, Bit Disappointed said:

Yes, it might. But one should consider, if one is more than a hobbyist and needs to process many RAW images, whether one should not run Photo on a Mac, where Photo offers to use Apple RAW as a converter. That was the 'hidden' point in my post, you can't work seriously having to go through and remember all sorts of workarounds. And most customers won't see them, probably only 1-2% of Serif's customers are here. 

@Bit Disappointed not gonna lie it is sometimes a burden, but i've gotten a lot faster editing sessions in AP over years and because this is the only thing i've had to have a work around for, and i have largely standardized it, it's not that big a deal. even for some pros (i'm a part time working toward fulltime), the adobe, capture one $240+ a year deal is a lot not to mention having to learn a new editor is a pain

[calebcudjoe]

6 hours ago, Ldina said:

Attached is the 32 bit, full sized afphoto file discussed in my previous post, with the embedded DNG. This DNG RAW file was intentionally underexposed to help me investigate whether channel clipping was a big part of the issue. It is. The AfPhoto file is HUGE as it is a full sized 32 bit file with additional layers (AP v2.4.0).

I've also included a small JPG export (sRGB) from the 32 bit file for those who aren't interested in downloading the above behemoth. This is fairly accurate to what my eyes see, but the sRGB color space loses some brilliance in those bright blues and cyans.. 

20240303-IMG_7067.afphoto 303.23 MB · 1 download

ok so i messed around with the "overexposed" one again as well as the underexposed one since i had yours for reference of the shade of blue, the overexposed is still the  better of the two, whilst i struggle to get the beautiful glow and on the fridge (could just be the angle) of the blue, the overexposed gives the best overall image in both our edits of these. i'll include my crazy adjustments on it; all corrections in photo persona in 16bit. i had to mask blue reduction with HSL on the sink as it showed too much blue.

In the edit file there are snapshots you can click through to see the before mask version or you can just turn off the HSL layer "sink correct" 

ok so i messed around with the "overexposed" one again since i had yours for reference of the shade of blue, tbh it is def the better of the two, whilst i struggle to get the beautiful glow and on the fridge of the blue it gives the best overall image. i'll include my crazy adjustments on it. i had to mask blue reduction with HSL on the sink as it showed too much blue.

In the edit file there are snapshots you can click through to see the before mask version or you can just turn off the HSL layer "sink correct" 

overexposed edit file.afphoto

[Ldina]

@calebcudjoe Caleb, the images of my espresso station were taken under difficult lighting conditions, partly on purpose. There was incandescent and fluorescent light in our kitchen, with cool, bluish outdoor light streaming in the window, so there was a lot of mixed lighting. And, of course, those radioactive LED blues. My main interest in choosing this terrible image was identifying what was causing the magenta/purple cast in the bright, saturated, blue/cyan LED lighting, then finding a way to deal with it. 

A lot of that magenta coloration is due to a severely blown out and clipped blue channel. (Sort of reminds one of the purple fringing around tree branches set against an extremely bright, contrasty sky.) The fact that the ICC model isn't perceptually uniform (especially with blues) simply adds to the purple problem. Even my Canon camera LCD shows a magenta cast. I opened this file in Lightroom and Photoshop too. Depending on which camera profile I choose, whether generic or custom, I end up with more or less magenta. Those profiles each have their own "flavor" and I'd wager that NONE of them are colorimetrically accurate.  

James Ritson has a few tutorials that deal with these sorts of issues. In one, he stays in 16 bit, but disables the tone curve in the Develop Persona, which makes it easier to address. In another, he had a night scene with bright lights (including a Hard Rock Cafe sign) where he processed the image in 32 bit. In both scenarios, it's generally best to slightly underexpose the RAW image to prevent much or any channel clipping in those bright lights. This way, at least the data is recorded by the camera sensor. If the data is completely blown out in 1, 2 or all 3 channels, it's usually more difficult (or impossible) to recover. 

I was able to fairly effectively deal with the purple cast in all of my exposures. The Affinity Develop Persona doesn't support custom camera profiles, so you cannot swap profiles to try out different "flavors". I don't really find that a problem, though I was used to using custom camera profiles in Lightroom and ACR. So, I left that purple cast in place in the Develop Persona, found a good tonal compromise, then dealt with final tonal adjustments in the Photo Persona, mainly with Curves (using Luminosity Blend Mode). I primarily used Selective Color, and if necessary HSL Adjustments, to deal with the purple. Whether you do that with a specific camera profile, or just the tools at hand, you are essentially doing the same thing. And yes, the sink has a bluish cast due to the mismatched outdoor light streaming through the window. 

I think most of this purplish issue is a camera capture issue, blown out channels (mainly the blue channel) and an ICC specification that doesn't do well with blues. If the Develop Persona could apply different camera profiles, it would deal with some of this just as LR/PS/ACR do. We just need to use a slightly different strategy. 

Perhaps someone will have more insight into this issue, but that's my take on it at this point in time. 

[Dan C]

Thanks for the further RAWs and feedback provided here! 

Testing these RAW files between Affinity Photo v2.4 and v2.1 (left vs right, respectively), there is a noticeable improvement in how the blue/purple tones are recreated when developing the RAW naturally (ie no changes applied) -

However, I can see that the Apple Core RAW engine is able to handle these tones even better than Serif LABs 2.4 - therefore I'll be providing these RAW images to our development team in order to help us continue to improve the RAW reproduction in Affinity, for a future update.

I hope this helps

[Ldina]

@Dan C Thanks, Dan! I look forward to future RAW processing developments.

Any chance camera profiles can be supported? (or is that a limitation imposed by LibRAW). As mentioned in the thread, different generic and custom camera profiles can yield very different results, particularly noticeable in those blues.

[Dan C]

On 3/4/2024 at 3:45 PM, Ldina said:

Any chance camera profiles can be supported? (or is that a limitation imposed by LibRAW). As mentioned in the thread, different generic and custom camera profiles can yield very different results, particularly noticeable in those blues.

I'm not aware of any specific limitation imposed by LibRAW regarding these, usually these 'Camera Profiles' are created by the camera manufacturer themselves and are created using, or including proprietary information / code that only the camera manufacture can correctly process.

Therefore support for Camera Profiles usually requires the individual camera manufacturers to work directly with the Affinity development team in order to include support for these - as I understand it.

We've previously had users request support for these Camera Profiles in Affinity and this is certainly something we'd love to add within Affinity, however I believe this would require the camera manufacture providing us the ability to convert and apply said profiles within Affinity.

Thus I would say that we don't have any direct plans for this currently, but we never say never

[Ldina]

@Dan C Thanks, Dan.

One can create their own custom camera profiles using various tools (Adobe DNG Profile Editor, X-Rite ColorChecker Passport, etc). I used my own custom camera profiles all the time in LightRoom, Adobe Camera RAW, etc. I had custom profiles for each of my camera models, and even some camera/lens combinations. These profiles improved color rendition. So, the camera manufacturer isn't involved at all with these custom profiles. 

I'm not positive, but I believe Adobe creates their own "sets" of generic camera profiles for different camera models by "reverse engineering" to come up with different "flavors" (Adobe Standard, Camera Neutral, Vivid, Landscape, Portrait, etc). Perhaps they collaborate with camera manufacturers, but I don't know. I always got the best results using custom profiles I created myself (usually dual light profiles, which utilized two exposures of a color checker...one taken in midday sun, and the other taken using tungsten incandescent light). I also had dedicated custom profiles for studio lighting. It improved color rendition and accuracy. 

Anyway, just some additional feedback in case this is something Serif is willing to consider. Different camera profiles can yield different renditions, and that came in very handy inside Lightroom with this "blue/purple" light issue. Some custom profiles were awful, and others were really good at dealing with blue light. FWIW.