Darktable negadoctor, flatbed scanner and Vuescan - choosing the proper input color profile

Processing
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I have been using Darktable for processing of my medium format C41 negatives using an Epson V800 and Vuescan. I use the image mode and scan to a raw (gamma 1 tiff).

I’m trying to figure out what the best input color profile to use for further processing. Using Rec709 linear seems to give me the exact look of the scanned negative, but the colors seem a bit dull (Kodak Ektar/portra film stocks).

If I use rec2020 linear, it seems the colors need too much correcting for the red level in the correction module.

I am using the color picker for the film base before any further processing.

If the entire negadoctor module is only optimized for DSLR scans, then I can look for some other software to process these as I am not interested in scanning that way.

Some information about the system and version being used:

System76 Thelio (Pop_OS 21.04)
Darktable 3.6 built to use the OpenCL (AMD GPU 5700)
Vuescan 9.7.65

Thank you for any assistance.

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I’m wondering if you couldn’t just scan a ColorChecker and make a profile from it with the same workflow as you’d use for a camera… ??

3

With my Minolta 5400 I actually made a profile for scanning slide (e6) with a fuji provia target.
Using that as input profile and then using linear rec2020 as a working profile actually works quite nicely… Although it sounds kinda wrong…

If the colors look dull but don’t need much correcting, it sounds fine as well. Nothing wrong with having to boost saturation a bit, very well possible your scanner produces lower saturation images allowing it to represent a fuller gammut.

I long gave up thinking in right and wrong when it comes to film negatives. Just more if I like the result and if one method is easier to do then another one.

Pick the output you like the most and is easy to do… Thats my 2cts.

1 Like
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Thank you guys for the advice. I have noticed some additional things since playing with this over the past year:

  1. If I choose a known pure black part of my image, not the film border, my color correction is far easier to accomplish. This is regardless of import color profile. I’m going to test this some more and suggests something incorrect about my film border color as darktable reads it. For raw/linear captures in Vuescan, I generally lock exposure on a piece of the border to ensure proper exposure of the frame (exposes to the right for the scan).

  2. I played with taking a photo with my digital camera of a negative and the color correction looked like more work, especially the dust/scratch work :slight_smile: