Saturday, December 26, 2009

A word of caution on using custom camera profiles

If you own a colorchecker, you can use DNG profile editor, or X-rite's passport Lightroom plugin to create a custom camera profile for your camera. This works really well. I should however caution you about an issue I discovered with this. One of the problems is that neutrals are not kept neutral when you change to a different camera profile in Lightroom or ACR. An illustration is given below.

On the left is the result of first assigning my self-calibrated profile generated using the passport plugin (this is also true for other profiles) and then using the white balance dropper on the neutral patch on the card and on the right is the result of first setting the white balance and then assigning the exact same profile. As you can see on the right, my very neutral grey backdrop turns green and the girl's skin is rendered a little too yellow. The skin tone might not be too bad but the green backdrop is very distracting I think. On the left, the color is just fine, no tint to the backdrop and good skin tone. The difference is simply in the white balance chosen by the white balance dropper. The image on the right, Lightroom chose 5700K and -3 tint, while on the left, it chose 5450K and +12. Quite a difference for white balancing on the same patch! I tested with all the other camera profiles and they all show this problem that there is a shift in the color temperature taken from the neutral patches.

P.S. if you prefer slightly more warm skintones than the very neutral rendering you get when using the neutral patch, the passport has a set of warming patches in the top row. You can simply select patches more to the right of the standard patch to warm up skintones. This results in the backdrop staying far more neutral but just the skintones warming up. A far more pleasant effect. See below for the result of choosing the patch two spots to the right of the neutral patch (the middle one in the top row of neutral patches. The second row of neutral patches also allows you to go to cooler colors and is more useful for landscape photography.

This made Lightroom choose 6000K and +27 tint. The skintone that resulted is very nice I think.

Conclusion: do your custom white balance after assigning the profile you want to use.

EDIT: It appears that this is mostly a problem with self-created dual illuminant profiles. I create these by shooting one image under tungsten light and another in sunlight as I don't own a calibrated D65 reference. Whether I create the profile in X-rite's passport program or DNG PE, they show the issue of neutrals not staying neutral. The Adobe-supplied camera-matching profiles also have the problem, but it is too minor to worry about. The differences in grey-card set white balance are on the order of 100K which you won't really notice.


  1. I don't quit understand how you consider this a "problem" and not the application doing what you ask. Changing the profile yanks the basic assumptions used by the white-balance eyedropper out from under it. It sort of sounds like you're saying "Be sure to crop to the size you want before you print, because otherwise, what you want will appear too small on the printed page and have stuff you don't want around it. If you crop first, this problem doesn't seem to happen."

  2. Jeffrey,

    I don't think it is quite that clear cut. Most people would consider white balance an absolute property that should not be profile dependent but only dependent on the illumination source in a well controlled system. You and I know that in ACR/Lightroom this is not the case and is slightly profile dependent but this is not general knowledge at all. This is evident from the myriad of confusion about the fact that Lightroom and ACR do not give the exact same color temperature values the camera registers in the RAW files but gives slightly different values for "as shot" than you will find in Capture NX, Canon DPP, etc. This is quite different from most other RAW converters.
    Also, according to Lightroom/ACR engineers statements, the way the DNG profiles are supposed to work is that neutrals will stay neutral whatever profile you select. There should not be a difference between first doing a WB and then changing the camera profile or doing it the other way around according to them. This is indeed the case for the built-in profiles. Any differences you get are less than 100K which you won't notice. What I ran into here is that this doesn't work correctly in self-created profiles. Probably this is the case because I did not shoot my daylight profile under standard D65 conditions but simply sunlight. Since this is how most people would do this, the issue might be encountered by more people.