Anyone using a scanner as densitometer?

Discussion in 'Scanning and Scanners' started by bvy, Mar 26, 2018.

  1. bvy

    bvy Member
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    If so, what's your workflow? I have a V500 scanner, a calibrated transparency step wedge, and an 18% gray card. I'm looking for a simple way to gauge density in my black and white negatives. I don't need lab precision, but I do want something quantifiable and fairly consistent. (Ideally I know I'd have a wedge or target on the same film base I was testing, but I'm willing to make some sacrifices.)

    Thanks.
     
  2. benjiboy

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    Don't ask me, I'm so analogue I'm having trouble using my V600 as a scanner :smile:
     
  3. Kino

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    Without custom profiles for each filmstock, you're not going to get meaningful densities from a simple scan.

    Scanners are linear/arithmetic imaging devices; negative densities are measured in logarithmic units.

    You'd be better served grabbing one of these for basic density measurements...

    https://www.ebay.com/itm/Vintage-Kodak-Color-Densitometer-Model-1/123034003911?_trkparms=aid=222007&algo=SIC.MBE&ao=2&asc=50998&meid=9aaa592d3c5c4bf797c87ae0a67a3c53&pid=100011&rk=2&rkt=2&sd=263343457222&itm=123034003911&_trksid=p2047675.c100011.m1850
     
  4. shutterfinger

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  5. Ted Baker

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    Its reasonably straight forward as the CCD is mostly linear. You will need to switch to raw, or remove the gamma (which you can do with a calculator). What software are you using? Do you have a step wedge to compare and calibrate? Depending on your answer will try and write some instructions.
     
  6. jim10219

    jim10219 Member
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    What are you using it for? I had an Xrite 301 densitometer and sold it because I had no use for such precise equipment, but did have a use for the money it brought in and the space it was taking up. These days, I use my flatbed scanner and Photoshop for measuring densities. But I use it for making curves for alternative processes. So in my case, I only needed relative consistency, not empirical accuracy. So long as my results were repeatable and predictable, it didn't matter if my scans were off. For darkroom wet prints, I'm plenty happy with trusting my own eyes. So the best way to go about this will depend on what you're needing to do with this information.
     
  7. Adrian Bacon

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    Yes. It’s fairly straight-forward. You need a way to get the average value of an area of pixels. I use a piece of custom software that I wrote that sucks in 16 bit tiff files and spits out the average r,g,b values of an area that I pass in.

    The other part is you need to be able to get the raw linear scan data with no gamma correction applied. Vuescan is good for this if using a flatbed, if using a dslr, dcraw is good.

    Once you have that, it’s just a matter of converting from linear to log. Assuming 16 bits, 65535 is 0.0, 32767 is 0.3, 16383 is 0.6, etc.
     
  8. Serg Lavrenchuk

    Serg Lavrenchuk Member
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  9. Serg Lavrenchuk

    Serg Lavrenchuk Member
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    Links to exl. file are dead ;(
    I have in a lab these files stored. If you undestand the system + have 21 step tablet = I could send it to email.
     
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