Curves

[varmsaus]

A curves edit window like in photoshop? Sorry for getting this from ai, but it's been a while since I used photoshop. I got excited when I found negpy, and remember this being an amazing tool for correcting film scans:

Photoshop’s native Auto Tone, Contrast, and Color commands often fail on film scans because elements like sprocket holes or uneven scanning backgrounds confuse the algorithm’s sampling. To automatically fix contrast and color on a 35mm scan containing sprockets, select only the exposed image area using a rectangular marquee tool, then create a Curves Adjustment Layer.

Hold Alt (Option on Mac) and click the Auto button within the Curves panel, then select "Enhance per channel contrast." This applies automatic color and tonal correction based solely on the selected pixels, ignoring the sprockets. You can then disable or delete the adjustment layer after flattening if you prefer a non-destructive workflow or wish to use it as a starting point for manual tweaks.

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It was especially the "Enhance per channel contrast" option that was useful.