DCamProf - a new camera profiling tool

[torger]

Thanks for the files. I've just made some brief observations. The camera is a 1DsIII, I'm assuming it's almost exactly the same as 5DmarkII so I used profiles for the latter as I have DCamProf profiles for it.

DCamProf makes no gamut mapping, Adobe Standard makes some small gamut mapping, but not very successful I think, just a quick compression towards the end which reduces the number of tones, then C1 gamut map quite heavily which is likely causing a bit of hue shift, red roses become more orange. The C1 rendering gives the impression of having most tones though.

I think what happens is that the red roses are so red that they glow, and in that red range the eye don't differ tones that well, so it looks less detailed. With the C1 gamut mapping the rose is less saturated and more orange and thus looks more detailed. C1's result looks quite similar to Trantor's SSF-based sRGB gamut-mapped profiles published in this forum a number of months ago.

I don't feel any urgent need to do anything with DCamProf in this area. A small gamut compression towards the edge like Adobe does seems to be a bad idea, and while the C1 more heavy gamut compression (Hasselblad's Phocus does similar things) can make better prints per default, it does distort color and it should be quite easy to do the same with post-processing techniques. But at some point I'll probably include gamut mapping features for those that want it.

[Bart_van_der_Wolf]

Thanks for the files. I've just made some brief observations. The camera is a 1DsIII, I'm assuming it's almost exactly the same as 5DmarkII so I used profiles for the latter as I have DCamProf profiles for it.

Yes, quite likely they are rather close.

DCamProf makes no gamut mapping, Adobe Standard makes some small gamut mapping, but not very successful I think, just a quick compression towards the end which reduces the number of tones, then C1 gamut map quite heavily which is likely causing a bit of hue shift, red roses become more orange. The C1 rendering gives the impression of having most tones though.

Some of the tulips are indeed extremely red (I also have some backlit ones that really glow as if lit from the inside), and C1 does have a tendency towards orange if the conversion is pushed in brightness in postprocessing.

I think what happens is that the red roses are so red that they glow, and in that red range the eye don't differ tones that well, so it looks less detailed. With the C1 gamut mapping the rose is less saturated and more orange and thus looks more detailed.

Possible, but the details can also be achieved by boosting the higher spatial frequency (luminance) amplitude (I use "Topaz Labs Detail" for that), but that's a different beast than achieving it through a profile look. These are samples of very saturated tulips, not the 'regular' colorful ones one will commonly encounter.

I don't feel any urgent need to do anything with DCamProf in this area. A small gamut compression towards the edge like Adobe does seems to be a bad idea, and while the C1 more heavy gamut compression (Hasselblad's Phocus does similar things) can make better prints per default, it does distort color and it should be quite easy to do the same with post-processing techniques. But at some point I'll probably include gamut mapping features for those that want it.

Yes, I prefer the control that postprocessing offers, but if a profile adjustment can get us further in the right direction, then that might require less additional work and maybe less noise amplification. At least you have some more images to test your ideas on.

Cheers,
Bart

[Frederic_H]

Ok, here the first results using a CC24 only. I'll work with the other charts later.

Except for the over-saturation and slightly reddish tint it's pretty close to what my eyes saw, much closer than the default P1 daylight profile.
Now I've to figure out what's going on with the reds, looking at the curve in Colorsync there's clearly an issue.

[torger]

Is the oversaturated look only in the reds? I'm on the mobile phone now (bad screen), but I get the sense that the DCamProf result is globally oversaturated. Could be some kind of problem in the patch reading process rather than make-profile make-icc step. If you PM me all data (including the cc24 raw shot) I can test on my side.

If it's a Leaf back there is a risk I need to make something different.

[Frederic_H]

It's globally oversaturated, needs -35 saturation or so in C1, regarding reds it's only some slight global cast.

The back is the IQ260, the phenomenon is the same with the aptus though. I've tried to use your CC24-ref.cie instead of my CC24 averaged spectro readings, and the red cast is a bit lower but still present.

I'm uploading data for you to have a look, will PM you the link.

[torger]

I will look when I get a gap. I have some social stuff I need to attend, in order to maintain my popularity among my nearest.

[Frederic_H]

Please do, nothing urgent on my side

I will play with the IT8 and DT targets this afternoon

[torger]

Got the files in PM, and I think I found the problem, the data does not get linearized as the transfer function is lost along the way (you got detailed solution in PM). DCamProf is not user-friendly so it's not a strange mistake to do. To the next release I'll make sure DCamProf aborts instead of just prints a cryptic warning in this situation.

[Frederic_H]

Good catch, that was it. I admit I didn't notice the warning.

So far the profile behaves quite well, thanks to it I've managed to get rid of that weird yellowish mess I had in a lot of pics.
Time to play with looks a bit, before some work with the IT8 chart.

Thanks for your work !

[Tim Lookingbill]

Don't know if it's due to the use of the CC24 target but I notice its familiar gradual roll off of shadow detail down to black in the foreground tree trunk on the right and the background trees as I get on DNG profiles with my camera using that chart. I do much prefer DCamProf's rendering mainly for its overall uniformity of color saturation and definition over the P1 Daylight version. And I can see the overly yellow cast in the brick wall on the left and in the tree foliage but it's a nasty dirty yellow.

But I don't know how that profile was constructed.

I'm impressed with the results. Good work, Torger.

[Frederic_H]

The dcamprof default neutral profile has been corrected since, here it is.
It clearly fixes that nasty yellow in the shadows on the left, and brings back the chroma of the rose building.

So yes, great job indeed 

[torger]

If the difference is very large between the bundled profile and the DCamProf result then one should suspect some error in the profile making process. As seen in the corrected example above the result is different but not huge, as Capture One generally makes decently neutral color, more neutral than Adobe does for sure.

As usual I'm not at my best screen (I'm moving this autumn so my work places are more chaotic than usual), but I think I can see that the main difference between P1 and DCamProf's result is that P1 is a fair bit warmer, ie more yellow. I've noted this in many bundled profiles, also Phocus for my Hassy warms up the colors a bit, but less global. I think a slight warmup in the green to yellow range can be an advantage for many landscape scenes (sunlit foliage) so I have that in the "look" example I provide in the tutorial, but I avoid applying it to blues, reds and shadows.

[torger]

Here's an high saturation flower example. Thanks to Bart for the test file.

With high saturation colors the differences between different profiles start to become quite large. The attached JPEG has a Prophoto ICC embedded and you most likely need a wide gamut AdobeRGB-capable calibrated screen to get good display result. The embedded thumbnail has no ICC, so you need to click to enlarge to get the correct image.

I'm focusing on the red roses here.

I noted that I got quite large difference between an older version of DCamProf 0.8.2, and the current one. This is due to some difference in the neutral tone reproduction operator. I'm going to look into this, because I think the older result is better. The older does clip quite a lot, but lowering the exposure (final image) the tones are nicely rendered. I think this is better than the sharper rolloff of the current version.

In terms of tone separation I think ACR and current DCamProf 0.9.7 is quite similar, but ACR is a bit less saturated and a more orange hue. C1 render has good tone separation, but is quite desaturated and very orange hue. DcamProf 0.8.2 dark has same tone separation as C1 but I assume more correct hue.

[Bip]

I agree with your analysis. Dcamprof 8.2 is more natural, Version 9.7 gives the idea of artificial color (Tulip) with too much saturation.
After, it is difficult to say which interpretation is faithful,

[torger]

Heh oh yes, red tulips of course, not red roses...

Anyway, concerning what is most faithful I don't know the original, but both DCamProf versions are in agreement of what the colorimetric color is, the magic happens when the curve and neutral tone reproduction operator is applied, it works a little bit different between 0.8.2 and 0.9.7.

When the color is so saturated that we're dealing with clipping it's much a matter taste what is most "faithful", do we want to compromise saturation (and possibly hue) to gain better tone separation or not? It's a bit like comparing "perceptual rendering intent" vs "relative colorimetric" when making prints. My guess is that DCamProf 0.9.7 is more similar to "relative colorimetric" (be as correct as possible as far as possible and then just clip, with a short rolloff to avoid the ugliest artifacts), while DCamProf 0.8.2 is more "perceptual intent" with more desaturation to improve tonality. There's no intentional "gamut mapping" in 0.8.2 though, so there's something else going on.

At the moment I don't know what causes the difference, but I'm about to dive into it.

[torger]

I now know what the difference between 0.8.2 and 0.9.7 is that causes the difference in look of the red tulips. Back in 0.8.2 the curve was applied in the luminance channel, but this was later changed to instead be "ghost-applied" in RGB-HSV and luminance taken from that (to get a more predictable/comparable result with a standard curve). Perhaps that was not a good idea, it does cause luminance separation to be reduced in this context.

I need to re-run tests on a bunch of images before I know if I can just revert it.

[Frederic_H]

Maybe we could have make-icc to automatically populate the ICC creator tag with dcamprof version number ?

[torger]

Just released 0.9.8.

Tested through my images and adjusted the tone reproduction operator accordingly so it renders saturated colors with better tone separation, like older version did. The look is not 100% the same as the old version, as there has been some other improvements on the way too.

I've attached a comparison, here all darkened to about the same level to make it easier to compare. Still a prophoto jpeg so calibrated wide gamut screen is recommended.

[torger]

Maybe we could have make-icc to automatically populate the ICC creator tag with dcamprof version number ?

It didn't get into 0.9.8... I'll look into it. I'm not sure it's okay by the standard, the creator signature should be registered I think. There's the copyright string and (set with -c "my copyright string") and description string (-n "my description") which you can set if you want to tag them yourself.

[Tim Lookingbill]

Just to test whether a wide gamut screen is necessary to view your posted sample I've uploaded a screengrab of the first attempt to confirm whether the red tulips of the DCamProf versions are suppose to have less definition and be on the slightly magenta side of red.

I'm viewing this on a Colormunki Display calibrated LG IPS 27" LED display with its profile embedded in the screengrab. I find the C1 the more realistic rendering and seeing its color issues described by torger.

Just a suggestion but I'ld find a test image having a wide range of saturated objects but exposed to look as real as the scene and not have over cranked color. I don't find this image as looking anything close to reality when it comes to flower rendering.