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I need to know what specific calculations Photoshop applies to an image when, using the gray point eyedropper in the Levels dialog box, I select a gray pixel in my image. Specifically, I need to know the algorithm the software applies to each of the R, G, and B channels in each pixel when a gray point is selected. For example, in a microscope camera software I use (Olympus Microsuite), when you select a gray point pixel, the software calculates the average 0-255 intensity value across the R, G, and B channels for that pixel. It then calculates a correction factor for each channel in that pixel by dividing the intensity value in each channel by the average intensity value. These correction factors are then applied to the rest of the image. So, for example, if the RGB values for the selected gray point pixel are (R,G,B)=(100, 200, 200), then the average intensity=100+200+200)/ 3=167. The correction factor for the R channel=167/100, for the G channel=167/200, and for the B channel=167/200. These correction factors are then applied to the rest of the image. Does Photoshop use this same algorithm, or something different? I need this level of detail for describing my methods in a scientific paper I’m writing. Thanks so much!
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