X-Rite ColorChecker Passport Dual Illuminant Profiles – Part 1
by Brenda K. Hipsher – May 14th, 2010
by Brenda K. Hipsher
Some of the most asked questions I get about ColorChecker Passport are questions about dual illuminant profiles. On one level dual illuminant profiles are easy to explain. But when I really start to think about it… not so easy. So we’re going to explore dual illuminant profiles in several posts over the next few weeks. We’ll do some experimenting and show you the results. Today I’m going to start with tungsten light as a singular light source.
On the same day with the same camera I shot the ColorChecker Passport in three different light sources, tungsten, shade and sun. I produced profiles for each of the individual light sources.
I applied the profiles to the specific images shot in the different lighting sources and applied a custom neutral to each one after applying the profile. I then processed the images and labeled them above.
For this post we’re going to concentrate on the tungsten light source and evaluate what different profiles produce when applied to only one image, the one shot in tungsten light.
Next I applied three different profiles to the image shot in tungsten light. Remember the profile for sun and the profile for shade were made using the images that were shot in that light source. But here we’re applying the sun profile to the image that was shot in tungsten light. And just as before we did a custom neutral before processing the images. Notice the very obvious shift from image to image above.
Next I produced a dual illuminant profile for sun and tungsten light and another one for shade and tungsten light. This must be done using the free standing software that comes as part of ColorChecker Passport.
This is accomplished by opening the ColorChecker Passport software and selecting “Dual Illuminant DNG” from the top tabs. I had processed two files to .DNG. I then drag first one and then the other into the window in the software window. Notice the two images at the bottom left of the large target. Once the images are placed into the software the “Create Profile” button is activated at the bottom right of the window. The profile is created and all you have to do is name it at the end of the process. First I produced a profile from the image shot in tungsten light and sun. Next I produced a profile from the image shot in tungsten light and shade. I named the profiles so that I could later identify what light sources were used to produce the profiles.
Finally I applied the single illuminant profile for tungsten light, the dual illuminant for tungsten and sun, and the dual illuminant for tungsten and shade. While there is still some minor shift from image to image, it is far less evident than what we saw with the single illuminant profiles applied. In fact the two dual illuminant profiles were very close to the single illuminant profile.
My evaluation is that the dual illuminant profiles seem to be a useful tool. In our next installment on dual illuminant profiles we’ll use the same process to look at an image shot in sunlight. Remember your ability to differentiate these images will be enhanced by viewing them on a calibrated and profiled monitor.
Stay tuned! And as always learn more about color management solutions like ColorMunki Photo, i1Display 2, i1XTreme, ColorChecker Passport and more at XritePhoto.com. Follow us on Facebook and Twitter to keep up with software updates, new product releases, Coloratti news, “how-to” blog posts and more!