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Problem with Optical density calibration-variation in formula function

Posted by Helene Hajjar on Apr 06, 2020; 10:22am
URL: http://imagej.273.s1.nabble.com/Problem-with-Optical-density-calibration-variation-in-formula-function-tp5023179.html

Hello,

I hope all is well.

I am following this protocol https://imagej.nih.gov/ij/docs/examples/calibration/ for Optical density calibration. How can I keep the same calibration for all the images I need to analyze even if I close and reopen the ImageJ software?

I tried copying and pasting mean gray values I got previously (in the Analyze/Calibrate dialog box, I copy/paste the 19 measurements of the step-tablet image into the left column with the OD values into the right column, I select "Rodbard" from the "Function" popup menu, I enter "O.D." into the "Unit" field and check “Global Calibration”). However, I get different values in the function formula “y=d+((a-d)/(1+(x/c))^b)”

I repeated the calibration while measuring mean gray values of the different shades of the step-tablet image and I obtained different mean gray values since I am not selecting the exact same spot of the shade.

How can I solve this problem?

Thank you,
Helene




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