Hi
I am in doubt about the purpose/state of this thread. Samuel, are you breeding on a common testing procedure ?
In the meantime, I have fiddlet a little with Iridient Digital and ColorPerfect, with the question: If I want to use CP, am I restricted to MakeTiff as the raw converter, or can I use e.g. Iridient?
Screen shots of the results in the zip.
My conclusion is yes I can use ID with my own linear profile. The canned profile of CP is good, as is my own, but not IDs default if linearised.
Hi Hening, apologies for my cyber silence. I got swamped with work this week but I managed to put some time in here and there to look deeper into camera profiles.
Let me first address ColorPerfect. I am struggling with its UI. But I am seriously shocked by how accurately its renders colors at its default settings (with the correct WB and white point settings), even with photographs of color targets - with no internal profile to skew colors to a few reference values, leaving us to think what's happening then to the rest of the colors. This I think we both agree on. There are other issues I have with CP. One of them that stopped me from going further with CP is that I cannot set it to render a completely linear tone curve. By design, it applies an automatic black point (BP). Look at this example:
I carefully set the White point correctly in both ACR and CP for this test, not so easy to do in CP! The entire image was remarkably similar tonally except in the shadows, and color rendering. The first image crop on the left is ACR's linear mode. The rightmost image is CP with its recommended BP setting, smartly calculated, may be unique to each image. The third image on the left is when I manually set its BP to zero. Second image from the left is ACR in linear mode, but with the Blacks slider at 5. Coincidentally, the default for Blacks in PV2010 is very similar to the minimum BP setting in CP. On checking with David, he informed me that I should never set the BP to less than 0.001, because of imperfections in image quality from sensors near the noise floor. With sensors performing as well as those on the latest Nikon, Sony and Pentax cameras, I'm not convinced that the BP clipping need be so high. Many photographers will disagree with me on this, and often they would want a strong black in their images and that's ok. For me I would rather decide whether to clip or not upon deciding my output medium, since printers are getting better and better at reproducing tones near black, and things get interesting there.
Jon Cone has an interesting article on that.You can certainly feed ID linear files into ColorPerfect, but David of course recommends MakeTiff. You must be able to get ID to output a linear gamma, unity white balance, non-profile tif to take advantage of Color Perfect's "color integrity", as it was designed.
Back to the profiles. Yes, your latest collection of CC photos all look quite similar, but with white point setting too high, I had to darken all the images to match the white patch reference value. That darkening may have skewed the colors a bit, since I had to work on a gamma corrected image, not a linear gamma version. Also, since this is a screenshot, your display profile may be doing unexpected things to the color.
I stress again that to properly make comparisons, we must first match the white patch to its reference value by setting the correct white point (figuring out which slider in different raw converters does this is not as hard as I thought initially), and set a custom white balance
after applying the profile, using the second lightest neutral patch of the CC. It will be unique for every profile (even in the same raw converter) but it is necessary so that the neutral patches are that - neutral. Then let everything else fall where they may.
But here is a synthetic CC overlay of your 2C=ID,-Canon_lin,-WP-adj-in-ID file:
Here is one of mine from ACR in "linear mode" and a custom profile from the DNG PE:
Here is another from Raw Therapee in "linear mode" with a custom profile that I built in Argyll using the arguement "colprof -v -y -qh -am -nc -u" in command line:
I'm not convinced that RT can handle dual table DNG profiles. It messed up with the same DNG profile that I used in ACR. One can set the preferred profile to Daylight, Tunsten, fluorescent or flash, possibly indicating that it is only using one table at one time. Btw this setting does not affect ICC profiles. This one is the "daylight" option:
This one is the "tungsten" option:
Caveat: These are all converted to sRGB for the web, and the cyan patch in row three is not correctly represented.
Here is a tif file (10MB), with all the examples in labeled layers, ProPhoto RGB, 16 bits.
I don't have access to a mac at the moment, but I think ID will handle DNG profiles correctly. I must try it out later. I would only be able to run ID in demo mode and cannot make a custom ICC profile for it. Might need some help with that.
I am surprised by how well the ICC profile performed. The ICC profile that I created was a simple matrix profile, with the -u flag in Argyll to "
avoid setting the white point to that of the profile chart". Additional information is
here. This, I am thinking, makes the ICC profile behave similarly to a DNG profile, assuming you strip the DNG profile of its LUT table. Not the tone curve, because the ICC profile will scale the patch values to the reference values in the matrix curves, effectively a "tone curve" as well.
I'm not sure what the DNG Profile Editor is using for its ColorChecker reference values, but I know for Argyll. It could be that that is causing the subtle differences we see here. Differing tradeoffs in designing the algorithms to map colors could also be another factor. Raw converter handling of camera profiles could also be involved. Many other factors that are not immediately obvious too.
Then there are many ways that one can mess up profile building doing the capture process (solarj is having this problem in another thread), and the profile building process. In the course of my testing, I discovered that the DNG PE is extremely sensitive to the placement of the four control points - slighly changing their positions will result in a visibly different profile. Sometimes hard to tell which is better, because some areas improve while others shift away from ideal. ICC profiling is too complicated to detail in this long post right now.
At this point I don't know if all this work is ever going to be justified. We still don't have luminosity based curve adjustments in the commonly used raw converters, including all the tone affecting sliders that affect a general image tone curve. I also disagree wholly with the results I am getting from ColorPerfect's "scientifically correct" method of saturating images, and I find Joseph Holmes's color variants to be far superior in many ways, not just the visible results. This all might work out in the end assuming that it works as it should, and the image processing pipeline does not introduce hue shifts at all, to invalidate the camera profile. Tough for the stars to align this way.
