3 Replies Latest reply on Jan 6, 2008 2:02 PM by Marco N.

    ACR Calibration - can't reproduce example


      I am trying to figure out how to calibrate my 20D. Unfortunate the sun is so low in Norway this time of year so I can't get a proper daylight exposure with the sun at 45 degrees up in the sky. Meanwhile I am reading Fraser/Schewes book about Camera Raw waiting for the summer. I do try of course with some images but not with great success.

      I played a little around with the scripts and I found this article where I found an example. I downloaded the image file _img_7409.CR2 and run the calibration with it. But I don't get the same good results as the example. Why?

      My errors (deltaE2000) is double the values of the example with Tindemans. I have tried fors/rags/tindemans scripts and all is different. I really don't understand why.

      Anybody else tried it and managed to reproduce?

      - Terje
        • 1. Re: ACR Calibration - can't reproduce example
          Marco N. Level 1
          Some questions.

          Have you downloaded the reference Lab file together with the image (CCvari.zip)?
          Have you founded the right RGB Prophoto values with the same software (GMB ProfileMaker 5)?
          Have you replaced the standard RGB values within the script?
          Have you tweaked the adjust tab in ACR before opening the image in PS?
          Have you setted the script like author?
          Have you compared the final results with the right Lab file (My-mini-CC-LabD50.txt)? The Rags reader works fine in this way

          In this article you can read the details of the author technic if you know Italian language or you can see the screenshots to found the right RGB target values with the freeware ColorLab together with the suggested script setup.
          • 2. Re: ACR Calibration - can't reproduce example
            Level 1
            Hi, and thanks for answering. I had not read your article so close and did not notice your changes to scripts and so on.

            I changed one of the script with yours values and saw better results.

            I am doing this for hobby mostly and is interested in camera calibration just for fun. I have a mini-colorchecker which I thought had correct colors. Therefore I could not see the need for calibrating the colorchecker also.

            If that is the case the hole calibration system is not as easy as just taking an image of the colorchecker and run the scripts. Then the need for calibrating the calibrater will come up and so on.

            But I will stick to standard values for my colorchecker and just shoot images with my 20D and run the scripts. I guess the colors will improve then too!

            - Terje
            • 3. Re: ACR Calibration - can't reproduce example
              Marco N. Level 1
              Some people has noted this and for this reason I have wrote the second article explaining the details of all passes.

              The Colorchecker has not to be calibrated but read with a spectrophotometer. This is an optional but if you want precision I recommend this pass.

              Conceptually, with some advices, the process is easy but the results and the research of precision sometimes carry frustration and waste of time even though using not commonly hardware and software.