How can I auto-correct color and contrast on film scans that include sprocket holes?

Question

I scan 35mm film with the sprocket holes visible, and sometimes the image extends slightly into the perforations. The scans come out flat, and Photoshop’s Auto Tone/Auto Contrast/Auto Color work reasonably well when I crop out the sprocket holes. But if I run those auto adjustments on the full scan, including the perforations and edge markings, the result is poor because the holes seem to skew the correction.

Is there a quick way to exclude the sprocket holes from the auto correction, while still applying the adjustment to the whole scan? I’d prefer an automatic workflow rather than building custom presets for each film stock.

xenoid · Answer

In Gimp I would do:

Using the Select by color tool (not the Wand), click in one of the sprocket holes (this should select all of them)
Select > Invert so everything is selected except the sprocket holes
Apply whatever auto-processing (which would also exclude any very dark spots in the image)

You can certainly do the same thing in PS.

How can I auto-correct color and contrast on film scans that include sprocket holes?

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