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X-Rite colorchecker theory


Ann Arbor, US
1267 posts

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Ruahrc Registered since 08th Jul 2007
Sat 11-Oct-08 05:56 AM

So I had a quick question about color management, calibration, and profiling.

A long time ago I borrowed a Spyder2 from a friend and calibrated (profiled?) my screen. The screen I use is a 15" Powerbook G4. That was almost 2 years ago, I'm sure the calibration has drifted a little since.

I recently ordered an X-Rite i1 Display 2 and while I was at it I picked up the X-Rite Color Checker chart. These are the two tools I need to get consistent color profiles across my workflow, right?

I received the colorchecker chart today, and tried it out. I went out and took a picture of the chart in the sunlight, and then took another from inside where the chart was lit by a tungsten bulb. Following the directions on the Adobe website regarding their DNG Profile Editor, I loaded the shots into the profile editor and had it generate the profile tables for the two charts. Then I saved this profile for use in LR2. The method I used was the two-shot profiling method which needs a test chart shot at 6500k and one at 2850k. Using the two pictures the DNG profile editor will calculate the correct correction values and also since there are two it will interpolate the corrections based on the measured white balance of an image.

(Note: to get DNG files from my RAW NEF files I opened them in LR, removed any correction parameters, and exported them as DNG files. Is this correct? Should I have white balanced the DNGs in LR to force them to 6500k/2850k values before exporting?)

Now, in theory, and provided that I have a properly calibrated screen, if I load up the picture of the colorchecker chart in LR and apply the profile I created in the camera calibration section, it *should* look exactly like the actual chart, right? Since the camera's sensor has been calibrated in the DNG Profile editor and the screen has been calibrated with a colorimeter, the color output on the screen should match exactly what I see in real life.

Looking at the colorchart picture in LR2 after applying the profile the colors are still not exactly matching to the real chart. I was actually surprised at how subtle the changes were going from the ACR default profile to the custom one I had just made. Maybe I needed to shoot it in more controlled conditions (the chart was not in direct sunlight, nor was the tungsten bulb shot a pure setup I'm sure either)? Where can I shoot the test charts such that they are under exact 6500k and 2850k lights? I don't have a studio or anything like that so I'm not sure I can get it good like that.

So I'm hoping that once the Display2 arrives and I re-calibrate my screen, I should then get color rendition that is pretty close to what I see on the chart in real life, yes? Or perhaps my display is simply too crappy to accurately show colors? Granted it's a laptop screen but as I recall the 15" displays on the Powerbook G4s were pretty good as laptop displays go.

Am I understanding what is supposed to happen with these pieces of color calibration hardware (colorimeter and chart) or am I missing something?

For the record I have a D80 and shoot RAW using the AdobeRGB color space. Does it matter what lens is used to shoot the color charts? I have the nikon 18-200VR and the nikon 12-24 f/4. Do I need to make color profiles for each lens?


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