"For example, I want the colors in the photo taken with ambient/artificial mixed light to match with those taken under CFL's at night." If that is what you truly want to do, then this product is not for you. A DNG profile is incapable of correcting for lighting that has very poor Color Rendering Index. This has little to do with inaccuracy of the target or software. You are just asking for something that can't be done with a DNG profile. The color checker passport target has a set of colors which closely align with the hue/saturation/luminance adjustments in Lightroom. They were put there just for situations that you are describing. That is where you make the adjustments that are needed when dealing with a light source that has poor rendering characteristics. It is not even clear to me that an ICC profile can be built to do what you are trying to do. I would be interested in seeing the results of actually using the target correctly. Go out in the early morning with your two cameras and photograph the Passport. Create the profile and compare the results from the two cameras after you apply the corrected profile. Don't compare the camera data to the reference values on the web site. Compare the camera data between the two cameras. Now you are testing the target with a reasonable light source that is rendering the scene very warm. Note that if you white balance the scene you will completely eliminate the warm appearance of the original scene. In your case, I would take up x-rite on their offer to refund your money. I don't think that you can utilize it for the task you mentioned. Regards, Tom Lianza On 9/20/13 12:18 PM, "Justin Krug" <jkrug@hotmail.com> wrote:
I was directed here by a helpful photographer whom I contacted regarding my issues with the X-rite Passport. My primary purpose for using it is to get accurate and consistent colors across different ambient and artificial light sources for architectural photography. For example, I want the colors in the photo taken with ambient/artificial mixed light to match with those taken under CFL's at night. Also, I wanted to use it to match color between cameras. On both counts, it has failed, and when I subjected it to a test using the reference values available on X-rite's website, it did not perform well. I would like to get some feedback from experienced members here regarding my findings and the response I received from X-rite after sending them details of my testing.
Here is an outline of my test: 1) I took the photo of the X-rite Passport under overcast daylight (no artificial light) with two cameras, the Canon 5d and Canon 60d. 2) Then I created custom profiles from each photo using the X-rite Passport software. 3) Next, I applied the custom profile to each photo of the Passport 4) White balance was corrected in ACR by clicking the WB on the square two over from black (#22) 5) Both photos were loaded into Photoshop and color sampler points were applied to the blue, green, red, and yellow squares (#'s 13,14,15,16) 6) The image was converted to Lab color and the a and b values were compared against the reference values on X-rite's website. 7) The same process was repeated for the photo from each camera using the Adobe Standard profile
What I discovered was that the color was just as accurate if not more accurate in the Adobe Standard profile. Also, the colors did not match between the Canon 60d and 5d after applying the X-rite profiles. A couple sample points from the Canon 5d (again, a,b values): Daylight overcast test-- X-rite: red a,b= 69,41; Adobe Std: red a,b= 61,37; Reference (rounded to nearest whole number): red a,b=53,28. X-rite: green a,b=-51,39; Adobe Std: green a,b=-47,36 Reference: green a,b= -38,31
I did the same test under artificial light (CFL I think) and the results were a little closer between the Adobe Standard and the X-rite, but for $100 and promises of accurate color, I was very disappointed.
After contacting X-rite, and sending over my findings and photos, I waited over a month to hear back, after their engineers were going to review my results. The response I received was surprising. X-rite said "To make a long story short, your standards for performance and data analysis would not be well suited to use ColorChecker Passport and its DNG profiles." And also "ColorChecker Passport software was designed to be a simple camera profiling solution for casual and non-professional photographers..." The recommendation was that I use an ICC profile as opposed to a DNG profile. They also offered me a refund on the Passport.
What do you think of my test and X-rite's response? Have you conducted your own objective testing? I don't need perfect color, but I do want consistent and accurate looking color. Thanks in advance.
-Justin Krug
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