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> You're going to have a hard time calibrating that without a whole bunch of patches with known reflectance/transmission profiles If you care about accurate co

> You're going to have a hard time calibrating that without a whole bunch of patches with known reflectance/transmission profiles If you care about accurate color, you do use a card with "whole bunch of patches" of different colors. For example, these British Library guidelines on photographing and scanning archival material say: "An industry-approved colour chart or greyscale reference card is essential in order to check the accuracy of the colour captured in the photographs. This is a physical card that is available to purchase on the internet. It cannot be downloaded from the internet and printed, or inserted into your image using software. Approved colour checkers that have been used in EAP projects include: Gretag Macbeth ColorChecker, QP cards, Kodak Color Control Q13 card, Past Horizons Bookmark Photo Scale." (https://eap.bl.uk/sites/default/files/Guidelines%20for%20photographing%20and%20scanning%20archival%20material%20%202017.pdf https://eap.bl.uk/sites/default/files/Guidelines%20for%20pho...) ColorChecker (“Macbeth”) Chart: https://poynton.ca/notes/color/GretagMacbeth-ColorChecker.html https://poynton.ca/notes/color/GretagMacbeth-ColorChecker.ht... QP cards: https://www.argraph.com/QP202.html https://www.argraph.com/QP202.html Kodak Q13: https://www.kodak.com/en/motion/page/color-separation-guides-and-gray-scales https://www.kodak.com/en/motion/page/color-separation-guides... Bookmark photo scale: https://www.pasthorizonstools.com/Photo_scale_bookmark_p/bookscale.htm https://www.pasthorizonstools.com/Photo_scale_bookmark_p/boo...

andreareina 5y ago
Thanks, forgot what they were called. Maybe the state of the art has moved in the ~10 years since I got out, or it's just the part of it I was in (fine art, prints for the magazine to reproduce (also forgot what those were called...)), but correcting to a color checker was manual and usually inexact anyway so I'd cue off of the grey and whatever thing in the image had a tone we'd have a strong expectation of how it should look (again, usually skin). As you quote they get used in archiving but those also tend to be done under well-characterized lighting and if not, it's something that's worth spending the time to tweak every little thing. It's a long shot from being able to apply automatic perspective and grey-point corrections plus a little bit of tweaking so the colors look "right" (or as right as possible under the wonky spectral distributions of most lights these days). I did manage to convince the company to buy the transparency so we could calibrate the film scanner's output.
bradknowles 5y ago
There’s a wide variety of photographic color meter light calibration charts, see https://www.amazon.com/gp/bestsellers/electronics/3109910011/ref=pd_zg_hrsr_electronics https://www.amazon.com/gp/bestsellers/electronics/3109910011... My favorites are from Datacolor or X-Rite.

andreareina 5y ago

Thanks, forgot what they were called. Maybe the state of the art has moved in the ~10 years since I got out, or it's just the part of it I was in (fine art, prints for the magazine to reproduce (also forgot what those were called...)), but correcting to a color checker was manual and usually inexact anyway so I'd cue off of the grey and whatever thing in the image had a tone we'd have a strong expectation of how it should look (again, usually skin). As you quote they get used in archiving but those also tend to be done under well-characterized lighting and if not, it's something that's worth spending the time to tweak every little thing. It's a long shot from being able to apply automatic perspective and grey-point corrections plus a little bit of tweaking so the colors look "right" (or as right as possible under the wonky spectral distributions of most lights these days). I did manage to convince the company to buy the transparency so we could calibrate the film scanner's output.

bradknowles 5y ago

There’s a wide variety of photographic color meter light calibration charts, see https://www.amazon.com/gp/bestsellers/electronics/3109910011/ref=pd_zg_hrsr_electronics https://www.amazon.com/gp/bestsellers/electronics/3109910011... My favorites are from Datacolor or X-Rite.