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Author Topic: LumaRiver Profile Designer - Gamut Compression question?  (Read 3203 times)

Redcrown

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LumaRiver Profile Designer - Gamut Compression question?
« on: June 03, 2017, 04:46:11 PM »

I've been playing with the LumaRiver Profile Designer (LPD) for a few days - making general purpose DCP profiles for use in Adobe workflow. I've made many different profiles varying one or more settings to see what difference they make.

That pointed me to the Gamut Compression settings under the Look tab. That variable seems to have the most significant impact on results, especially on images with bright, highly saturated colors, which is no surprise. But I'm a little confused by my test results.

The following sample shows results of each compression method on an image with those pesky reds that often fall outside sRGB and Adobe98. This sample is in sRGB for web posting, but was constructed in ProPhoto 16bit. Please trust me that the sRGB sample looks reasonably close to the ProPhoto image inside Photoshop.

Look first at the lower right corner, which is the LPD "no compression" version. In my opinion, it is the worst. Much detail is lost, colors seem to blend into a solid mass. I expected the opposite. The sRGB Strong and Adobe Strong version on the top seem the best. Plus, those versions seem almost identical, which surprises me. Assuming the raw values are out of gamut for both sRGB and Adobe98, I'd expect "compression" into those spaces to show significant differences.

Further confusion comes when I process images with reds that are far less bright, and a little less saturated (maybe within gamuts). In those cases the LPD "no compression" profile generates better results (more detail retained) than either of the sRGB/Adobe compression versions. Converting the no compression version into sRGB within Photoshop retains the detail and looks much better than a version that was compressed by the LPD profile.

So, I'm looking for advice or experience of others. How do you interpret the LPD gamut compression options? What is a best practice?



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scyth

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #1 on: June 03, 2017, 09:21:28 PM »

...

I'd keep it in one topic though...
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torger

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #2 on: June 04, 2017, 04:56:09 AM »

In an ideal world the raw converter rather than the profile would do the gamut compression. Then it could adapt compression depending on image content. If there are no high saturation colors, it would have no compression. No compression of course looks best when all colors fit in gamut. In high saturation no compression will yield colors that clip, and you loose details.

The problem is that raw converters don't have realtime subject-dependent gamut compression, so you have to make a tradeoff in the profile. The safest way is to put pretty strong compression in there so you get good rendering with high saturation bright colors, but this does not come for free as you have noted. In order to make a smooth transition from low to high saturation you cannot just have a sharp compression in the end (then gradients would look bad), but you must start compressing also for pretty normal saturation colors. In other words you get compressed tonality compared to the "no compresison" mode.

The difference between sRGB and AdobeRGB targets is small, the difference between Strong and not is much larger. The sRGB/Adobe mode only works on the chroma axis, while Strong adds a HSV-Value compression too to reduce clipping. The thing is that clipping is mostly due to too bright colors rather than too saturated, so the Strong has a much stronger compression effect. This is also why the difference between sRGB vs AdobeRGB targets is so small -- less happen on the chroma axis than one may think. It's not a zero difference though which one can see when studying closer.

An interesting observation is the "cheating" Adobe Standard does. The tonality in their result is good I think (Almost as LRPD AdobeRGB-Strong close to clipping, and perhaps a bit smoother in clipping), however partly by putting lots of green into reds making them more orange. This way you get less clippy bright reds, and more stability when clipping, at the cost of incorrect hue. Pushing hues towards green is a common method made in many commercial bundled profiles, not just Adobe (makes it possible to make brighter colors with less and more stable clipping). With Lumariver Profile Designer the goal has been to not cheat with the hues though, which makes the compression task a bit tougher. There's still a small cheat with the hues with LRPD too, with strong clipping reds you will get a shift towards orange, this is needed to make subjects like sunsets look good, some more tonality is also retained.

The default is set to "AdobeRGB-Strong" and that is what I think most people will think is the best tradeoff if you're making only one profile. However, if you have the possibility to change profile depending on subject, having an extra profile without compression is a good idea, so you would use that when there's little or no clipping issues, then you get better tonality in medium-saturated colors.

If you go advanced and get into tuning hue errors in the optimizer you could also look into pushing reds towards warmer rather than cooler (if that's not already the case), this adds some extra stability.

I have worked a lot with the gamut compression algorithms, and I may be doing even more work with it in the future. There will always be tradeoffs though, which is in a way what makes profile-making fun, and also what makes it valuable to have your own profile designer and not just relying on pre-made profiles by someone else. I've personally been using AdobeRGB-Strong compression, but I'm more going towards using "no compression" for subjects that don't need compression, and as my personal shooting style is pretty low on saturation that makes up 90% of my pictures. Would I shoot a lot of colorful flowers though, I'd use gamut compression all the time.

Sliders in the raw converter also allows you to manually control the gamut a bit, then one should generally first try to reduce brightness/lightness rather than saturation of the clipping hue. But then you need to do manual stuff per image. What suits you the best depends on what type of subjects you shoot and what type of post-processing you do. The all-around "just works" mode I'd say is the defaults "AdobeRGB-Strong" though.

I hope this helps.

(Oh one more thing -- I should say that gamut compression in camera profiles is not like gamut compression (or rather gamut mapping) in printer profiles. In printer profiles you map from one fixed gamut to another fixed gamut. In camera profiles you don't really know what colors you're going to get ("cameras have no gamut") and also the output gamut varies, so less exact, more perceptual and less mathematical methods need to be used.)
« Last Edit: June 04, 2017, 05:24:29 AM by torger »
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GWGill

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #3 on: June 04, 2017, 06:49:08 PM »

(Oh one more thing -- I should say that gamut compression in camera profiles is not like gamut compression (or rather gamut mapping) in printer profiles. In printer profiles you map from one fixed gamut to another fixed gamut. In camera profiles you don't really know what colors you're going to get ("cameras have no gamut") and also the output gamut varies, so less exact, more perceptual and less mathematical methods need to be used.)
Note that while this is true of many print or screen display workflows which process images encoded in output rendered colorspaces , it is not so appropriate when images are encoded in large gamut colorspaces such as ProPhotoRGB, L*a*b*, scRGB etc., where there are very similar issues to that of a Camera workflow that is dealing with un-rendered images. But not all output workflows are limited in this way - ArgyllCMS allows per image gamut mapping to be used in print and screen ICC based workflows, and there is a nice synergy between using per image mappings and using higher quality device link transformations.
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Redcrown

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #4 on: June 05, 2017, 02:15:42 PM »

Torger,

Thank you for the detailed reply. Very helpful.

But it brings up another question - when are you going to write a raw converter that fixes the deficiencies in the existing products?
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BartvanderWolf

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #5 on: June 05, 2017, 02:22:42 PM »

Torger,

Thank you for the detailed reply. Very helpful.

But it brings up another question - when are you going to write a raw converter that fixes the deficiencies in the existing products?

I think Anders only likes challenging projects ;)

Cheers,
Bart
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scyth

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #6 on: June 05, 2017, 02:53:24 PM »

But it brings up another question - when are you going to write a raw converter that fixes the deficiencies in the existing products?

people behind rawdigger & fastrawviewer products set their eyes on a raw converter now ( https://blog.lexa.ru/comment/47790#comment-47790 ) ... but the code will be only working on GPU with OS/drivers supporting at least OpenGL3/DX11 +

now that (not GPU bound mind you, the people) shall bring some features
« Last Edit: June 05, 2017, 04:04:25 PM by scyth »
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torger

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #7 on: June 05, 2017, 03:59:55 PM »

I've contributed a bit to RawTherapee, that's all. Raw Converters are sure challenging enough :) , but there's many good out there, while there wasn't that much for profiling.

A thing with raw conversion is that you need to spend a lot of time to make algorithms fast, really a lot of time. I'm really impressed with what skilled people can do regarding optimization (fastrawviewer mentioned above is a good example, but also Lightroom), but I personally don't find that much enjoyment in that kind of programming (so excuse me for LRPD being a bit slow...). Making a speedy raw converter is about 20% making the color algorithms, and 80% making them run fast. My skills and interest is then better suited for profile maker software where you really can concentrate on the result of the color algorithms and not having to compromise to make them run fast.

One reason that there's no real-time gamut compression out there (what I know of) is that it's probably still quite difficult to make them run fast and look good at the same time. It should not be impossible though, so I guess there's also a lack of interest, why I don't know.
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Ghibby

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #8 on: June 07, 2017, 08:28:27 AM »

Hi all,

This topic follows on nicely from the OP of this thread as it concerns colour gamut but in a high luminance / highlight clipped scenario.  I am very interested in LRPD and have been experimenting with it to deal with an issue that occasionally pops up in architectural photography scenarios with lots of LED lighting, especially with blue LEDís.  The issue as you can see below is how the camera profile deals with intense blue colours and detail rendition / retention when these are close to or beyond clipping.  My current method of dealing with the issue is by using a dual illuminate base profile I created in Adobe DNG profile editor. This was created with the colour checker passport and using a base profile of Camera Neutral with the standard Adobe ACR tone curve. The result is a profile very well suited to editing in LR or ACR as it is low in contrast, with good colour separations plus forgiving of highlight and shadow manipulation in high contrast images.  I feel the way the Adobe standard profile (and subsequent Adobe Standard V2 for the EOS 5Ds) is not ideal, over saturated colours and tonal transitions that are not subtle enough to my eyes. The Adobe cam neutral profile is more successful except for the hue shift of saturated blues into a more purple hue, my profile is a tweaked version of this.  When combined with a little adjustment of the blue lightness and hue sliders in the Calibration panel of Lightroom it is usually possible to get a very nice looking result that is perceptually close to the scene and resolves the blue to purple hue change quite successfully. I am not concerned in preserving faithful colour accuracy in these scenarios just a good looking rendering of the scene. 

I have applied a similar logic to creating a profile in LRPD and so far I am not even close to getting the results I want.  See attached images showing screen grabs of a test image that replicates a similar scenario from a Xmas decoration of blue LEDís.  The profiles uses are the labelled on the images clearly and as you can see the Adobe ones all seem to render a far more pleasing result in terms of detail retention and more significantly tonal transitions of colour, especially where it has clipped and then transitions into areas where only the blue channel clips.

I have also tried playing with the look adjustments panel and tweaking several colour patches but I can't seem to achieve a look I am happy with or one as smooth as the Adobe derived profiles.  Any suggestions on what is causing this behaviour and how it can be effectively dealt with? My suspicion is that the core issue is caused by the blue channel clipping and the red channel having barely any information, evident by high levels of noise in the red channel when you analyse such images carefully. The big question I have is whether LRPD can generate a profile that will give the nice smooth transitions of the Adobe Cam Neutral profile while avoiding the undesirable hue shift in the blue channel?




« Last Edit: June 07, 2017, 08:45:33 AM by Ghibby »
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scyth

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #9 on: June 07, 2017, 08:56:08 AM »

especially with blue LEDís. 
those are static scenes, no ? slap a filter on lens to balance raw channels and profile for it.
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Ghibby

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #10 on: June 07, 2017, 09:34:58 AM »

Not a useful thing when the blue LED is a small part of the scene such a retail signage, balustrade up light, kills the quality / tonality for other mixed light sources. 
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scyth

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #11 on: June 07, 2017, 09:56:20 AM »

Not a useful thing when the blue LED is a small part of the scene such a retail signage, balustrade up light, kills the quality / tonality for other mixed light sources.

you allege that you have a great disbalance between blue and red channel saturation in raw - it does not matter that blue LEDs take just a small part in your frame - you either clip the blue channel ( and you do not wish to lose the details there in that same area when blue LEDs are, do you ? if you do then I am sorry ;D ) or undersaturate the red channel in the whole frame ... so gel the light... now if you also have red LEDs too then it might be more complex ... if you think that spiky spectrum of the led can't be helped that way then Eric Chan from Adobe suggested a simple way - pull back blue channel saturation in "camera calibration" tab of ACR/LR ... you are not after exact colors anyways and that helps
« Last Edit: June 07, 2017, 10:04:47 AM by scyth »
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Ghibby

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #12 on: June 07, 2017, 10:48:33 AM »

All I am after is the ability to create a profile to deal with complex mixed lighting sources, simply not interested in using filters / gel to solve this problem. As mentioned in the first post I made in this topic I can deal with the issue successfully in LR by using the profile I created in Adobe DNG Profile editor plus as few tweaks to the calibration sliders as well as the HSL sliders.  My mention of an in-balance between R and B channels in the raw file was only a speculation on the cause of the banding / tonality issues in the example images I posted, ie that in any area dominated by bright blue light is by inference going to be low on the amount of exposure to the Red channel (and to a lesser degree the green) in these areas of the frame. 

It would appear the LRPD has the most comprehensive set of tools available to manipulate / design profiles and with this level of control I am hopeful that the comparatively simple profiles that can be created in Adobe DPE can be drastically improved upon.
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scyth

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #13 on: June 07, 2017, 11:08:23 AM »

All I am after is the ability to create a profile to deal with complex mixed lighting sources

no such fish as that kind of universal profile for all "complex mixed lighting sources" really...

the cause of the banding / tonality issues

the source is LUT and/or how the data is compressed to fit in some proper colorspace by a code inside a raw converter  ... you can't fix the code (only change the converter)... you can either fix the LUT or help the LUT/code by manipulating with pre LUT matrices (like what Eric Chan suggested - which is the quick fix for almost any kind of profile)... because you are shooting in the dark (S/N poor in most of the frame) and again you are not trying to clip areas @/around the sources of bright lights I 'd suggest simply to go with matrix only profiles and such as that desaturate the "colors" during the color transform... the most simple way to get such profile is simply to strip all LUTs from profile like Adobe Standard (because Adobe designs matrices in their profiles that way nowadays) using dcptool or dcamprof command line tools...



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Ghibby

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #14 on: June 07, 2017, 12:03:04 PM »

My post really was a question asking why the tonal gradations rendered with the profile generated in LRPD are not as smooth and detailed as those by Adobe in extreme lighting scenarios.  The adapted Cam Neutral profile comes pretty close to dealing with mixed lighting sources to a level I am happy with, all I want to do is negate the heavy purple twist in the blue channel, or better still find a way to make LRPD outperform Adobe DPE in this instance.  Do not look at the example image as the type of image I am trying to create, it was shot purely to illustrate the banding / tonality issue I want to resolve in LRPD.
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scyth

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #15 on: June 07, 2017, 12:12:21 PM »

My post really was a question asking why the tonal gradations rendered with the profile generated in LRPD are not as smooth and detailed as those by Adobe in extreme lighting scenarios.  The adapted Cam Neutral profile comes pretty close to dealing with mixed lighting sources to a level I am happy with, all I want to do is negate the heavy purple twist in the blue channel, or better still find a way to make LRPD outperform Adobe DPE in this instance.  Do not look at the example image as the type of image I am trying to create, it was shot purely to illustrate the banding / tonality issue I want to resolve in LRPD.

if you want the author to take a look may be you can also post both the raw file itself + the profiles (Adobe mod and LrPD one) you use ? my $0.02
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Ghibby

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #16 on: June 07, 2017, 07:28:05 PM »

scyth a good suggestion,

We Transfer link below contains the DNG sample image, my modified Cam Neutral profile as well as the DNG files of the Color Checker Passport used to generate the profile. These are the same images used to generate the Adobe Profile in the link too.  I have not yet purchased LRPD, my observations are based on the demo version in Pro mode so not possible to create / export profiles in this guise.

LRPD Evaluation Files

Be interesting to see if this is within the scope of the software.

Ben
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GWGill

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #17 on: June 07, 2017, 08:08:31 PM »

All I am after is the ability to create a profile to deal with complex mixed lighting sources
No  raw converter or profile can fix that - it's a property of how close to a human observer the camera spectral sensitives are. You can change that a little using filters, and you can change the size of the errors somewhat by changing the lighting, but the profile will only let you trade errors in one image spectral element for another.
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torger

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #18 on: June 08, 2017, 05:09:07 AM »

I will need some time to look into that, I can't give a quick response.

LRPD does have issues with artificial blue lights especially with cameras with high blue sensitivity. I haven't really gone to depth with how to fix the issue through custom design, I'll have to look into that separately.

The reason there is an issue in the first place is that there is a tradeoff to make. In order to have normal saturation for normal blues and not have too sharp/steep compression curve there must be a compromise, and that compromise here is to cut artifical blues (=unnaturally high blue signal in relation to red and green at the raw level) hard and sometimes ugly as there's really no space to make a transition. Otherwise you have to desaturate way into the normal range, and preferably turn that whole blue hue range towards cyan, that is compromise both saturation and hue. This can be seen in some of Adobes stock profiles (A7r2 if I remember correctly), and those profiles are great in those special conditions where LRPD comes in short, but doesn't really render that accurately or even pleasing in normal conditions, where instead LRPD excels.

So the question is, can you using LRPD's design tools make a profile that makes that other type of tradeoff? I need to test that and see, I don't know for sure. Normally the design tools are used to make quite small adjustments rather than huge changes, and this change would classify as "huge".

In any case you can't fit all the tradeoffs into one profile, you will have to use one profile for normal conditions, and another for those special conditions.

Many bundled profiles are designed for robustness in all sorts of conditions to be as "user friendly" as possible, and thus are forced to make some compromise in rendering performance for normal conditions. In LRPD I've chosen the approach to be as robust as possible, but without hurting performance in normal conditions, and that blue issue you see is a result of that design approach.

One idea for a new feature could be to make some sort of "extreme" gamut compression designed for this specific use case. What all this narrow band light stuff is about is to avoid that extreme raw saturation lead to clipping and work backwards from there. You will end up with compromised rendering in the normal range, so it would be a special mode for this specific need.
« Last Edit: June 08, 2017, 05:30:01 AM by torger »
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Ghibby

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Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #19 on: June 08, 2017, 08:21:06 AM »

Hi Torger,

That makes a lot of sense. I assume the same behaviour will be apparent for bright artificial lighting in all of the channels with less effect in the Green due to double the amount of area sensitive to this due to the bayer design of most sensors.  All I would be looking for in the way a profile deals with such lighting is for there to be a nice roll of into the clipped or gamut strained areas, even if this is at the expense of pure colour accuracy.  A more typical scene where such issues are apparent can be found in the link below, architectural scenes with a component of intense blue lighting in the sign and illuminated sofitt area, otherwise they are primarily lit with various artificial light sources. In these cases the profile needs to be able to render an image that is natural looking but with nice roll of the the extremes.

Perhaps an additional setting withing the gamut compression set to deal with extremes of hues or perhaps a targeted highlight roll off parameter could be employed to deal with these extreme examples of lighting. While they are are probably not so much use for landscape shooters for the architectural crowd this could be an extremely valuable parameter to be able to control.

Sample DNG scenes

I have also had a brief play my cam neutral profile in Adobe DPE and shifted the blue colours hue away from the purple end of the spectrum and managed to create a much more pleasing result, it would appear initially without much compromise to the green and red hues, however this is based on minimal testing or image comparisons as yet, I'll keep plugging away. This is done by manual visual adjustment of 5 or 6 hues in so not exactly a scientific approach. 

Thanks for your help. 
Ben
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