[sane-devel] Scanner Driver Interface Bit Depth

[Nicholas Andre]

Hey!

I’m using an Epson V850 to scan color negative film. I’ve been able to use
XSane and Epson Scan. Color negative film has a fairly low DMax and as a
result the dynamic range of the physical material must be expanded to
produce a digital file with correct contrast.

Basically what I want to understand if I improve my bit depth fidelity by
transmitting context about the desired output image to the scanner.
Essentially the difference between:

1. Ask the scanner for the full raw image with 16 bit depth with no
histogram or gamma adjustments and do all the work afterwards with the 16
bit file.
2. Instruct the scanner which segments of the dynamic range I care about
(eg the lightest and darkest regions of each color channel).

I see for example in the epson2 driver I can see that some parameters seem
to be forwarded:

Halftone
Brightness
Film type
Gamma

Which of these options (if any) provide material benefit to the output if I
can set them up front? Or alternatively whether it’s simply a software
calculation and it doesn’t matter if I scan every image uniformly and
process them after?

Essentially I’m trying to glean whether the epson scanner will adjust
calculations up front based upon driver inputs (analog gain/exposure or
internal processing of higher bit depth material)

—Nick
-- 
Thanks,
Nicholas Andre
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