Curves behavior with a negative scan

Question

I'm wading into scanning my mostly black&white negative archive. Haven't done much before now, but the scope has me curious about simplifying the correction process inside PS. If it was just an occasional scan I'd deal with it, but with the number of scans involved I'd like to standardize on familiar behavior.

My Epson V750 scanner and Epson Scan 2 driver are working well enough, and yield a POSITIVE image and thumbnail upon viewing in Bridge and PS. But it's always bugged me that the curve behavior is opposite of all my other experiences with positive scans and digital camera files; that is, pulling down the left end of the curve LIGHTENS the displayed positive image and pushing up the right end DARKENS the image. So even though it's displayed as a positive, the curve is acting as though it's a negative.

Is there a way to have curves behave as it does with other non-negative files?

Thanks in advance.

Semaphoric · Accepted Answer

Look in the Properties panel menu, and select Curves Display Options. You apparently have Pigment/Ink % selected. Try changing it to Light (0-255)/

Conrad_C · Answer

In the posted screen shot, the menu above the Curves graph says Gray. I think that’s probably the explanation, and if it is, the graph is working as expected, and as Photoshop has worked since the 1990s.

How the Curves graph displays depends on whether the color mode is transmissive or reflective. In transmissive light modes such as RGB, 100% equals full brightness and all channels maxed out makes white, so in Curves, the top and right sides (maximum values) represent white. In reflective (print) modes such as CMYK and grayscale, 100% equals full ink coverage creating black, so in Curves, the top and right sides represent black.

Accordingly, the histogram inside the Curves graph appears follows the orientation of the tonal values. So in the picture below of the same image, when the image is gray (on the right), its histogram appears reversed compared to when it’s in RGB (left).

It looks like the Epson software was probably set to save the scans in a gray color mode, so Photoshop uses the “100% equals solid black” graph in Curves. If you converted it to an RGB color space or had the Epson scan software save them in RGB, the graph would invert to the transmissive model that you might be more used to.

Lightroom always uses an transmissive light graph, because it does not support ink-referred color modes (you can’t edit in CMYK or gray).

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