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I want to take photos of a few surfaces (wood floors, bricks, etc.) then print them, matching the colors of the actual object (in whatever the lighting conditions are at the moment) as closely as I am able. (I'm building scale models of things.) I don't have any professional photography equipment, just an old point-and-shoot and I guess my phone. Fwiw, neither of my cameras provide raw image files.

I do have an accurately-enough calibrated monitor and printer. Currently both are set up to render AdobeRGB color data. I tested the printer by printing a variety of pantone color swatches and comparing them to physical paint samples of the same color. The paper I'm printing on is satisfactorily white and opaque, and the printer calibration covers the printer + paper.

But, I'm not sure how to capture the colors accurately with the camera. I'm also not sure how to identify and/or control the color space of the image the camera stores (unnecessary diagram, not worth inlining).

Now, I don't need super high accuracy, just... decently close.

What I am thinking of doing is:

  1. Print a small card with cyan, magenta, yellow, and black gradient strips, each fading to white.
  2. Place the gradient card in the shot.
  3. Set camera white balance to auto, I guess?
  4. Adjust camera settings to get histogram as wide as possible without clipping blacks or whites.
  5. Take picture.
  6. Then, in software, tweak the image until the gradients on the card are correct (according to the software, not the monitor + my eyes), making sure to work and save in the AdobeRGB space.
  7. Print.

So my questions are:

  • Will that work? It seems like it should, except:
    • I feel like my step 6 somehow "cancels out" the ambient lighting conditions (like... since I'm taking a known color, exposing it to arbitrary lighting, then transforming the whole image back to that known color... I can't really explain why I think this it's just a gut feeling... and maybe it's what I want to do anyways since if I print that then view the printout in the same lighting conditions, then that gets reapplied? Although the white balance messes up the lighting anyways... I wish I could state this in a more sensical way :S ).
  • Is there an easier way given equipment limitations?
  • How is it normally done (if I had access to better cameras, color measuring thingies, etc.)?
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    \$\begingroup\$ All I can think to say is, "Oh, if only it were that simple". ;) \$\endgroup\$
    – Tetsujin
    Oct 20, 2021 at 16:06
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    \$\begingroup\$ Kind of. First of all, measuring colour by eye is really, really difficult. 2nd, you don't actually know how good [read 'flat'] your lighting is, then you don't know what your camera will do to that. You can't print from AdobeRGB to CMYK with anything other than guesswork & you then look at the print in more uncalibrated lighting. It's tough. \$\endgroup\$
    – Tetsujin
    Oct 20, 2021 at 16:15
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    \$\begingroup\$ What photo editing program(s) do you have? I'm thinking you could do a post processing white balance adjustment by shooting a calibrated grey card. Better is Macbeth chart color calibration. \$\endgroup\$
    – qrk
    Oct 20, 2021 at 16:19
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    \$\begingroup\$ Again, it's an unknown. Lighting can be measured for accuracy using a structure known as CRI Colour Rendering Index which is another minefield ;) \$\endgroup\$
    – Tetsujin
    Oct 21, 2021 at 8:53
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    \$\begingroup\$ Printers simply cannot reproduce even the relatively limited gamut of sRGB, let alone Adobe RGB or Pro RGB [which actually goes outside human perception & cannot be even reproduced on a screen] \$\endgroup\$
    – Tetsujin
    Oct 21, 2021 at 16:59

3 Answers 3

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Lighting is the place to start. You want a very high CRI for color critical work. Tungsten hot lights are the most accessible way to get that.

Second piece is an accurate gray card.

Third piece is a camera that allows setting the white balance off the gray card.

But with a good tungsten bulb, the color temperature will be right at 3200k.

If you use LED’s or fluorescent sources, you won’t have full spectrum and some colors will always be off. Xenon flash/strobe tends to have some variation in temperature, though it provides full spectrum.

Without a known light source, everything about the input is more of a guess.

Light sources for viewing printed colors is a whole higher level of specialized equipment with prices to match. But that’s a mostly a waste of resources without accurate input.

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  • \$\begingroup\$ When taking the photo, does calibrating against a white + gray + black card compensate for nonideal lighting? Under the assumption that the spectral coverage of the light is fairly complete I mean (as in, not sodium vapor lamps or something like that). \$\endgroup\$
    – Jason C
    Oct 21, 2021 at 22:37
  • \$\begingroup\$ Actually does the lighting even need to be full visible spectrum or does it just need to cover the combined spectrum of the camera sensor elements? This might be a separate question. \$\endgroup\$
    – Jason C
    Oct 21, 2021 at 22:42
  • \$\begingroup\$ @Jason C If the light is not full spectrum, materials can not reflect the missing frequencies. The human visual system (our eyes) can and do see colors in the gaps do to the way out visual experience is constructed by our nervous system. On the camera, all visible frequencies can be defined in terms of red, green, and blue (or X,Y,Z in the general case). The science of human visual experience is complicated, messy, and wet. But it is a science. \$\endgroup\$
    – Bob Macaroni McStevens
    Oct 22, 2021 at 2:19
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    \$\begingroup\$ @JasonC Tungsten hot lights are not expensive and because there are sensible tradeoffs favoring LED for many applications, used tungsten fixtures are even cheaper. \$\endgroup\$
    – Bob Macaroni McStevens
    Oct 22, 2021 at 16:07
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    \$\begingroup\$ @JasonC camera sensors are sensitive to the entire visible spectrum as well as adjacent parts of the UV and IR. Typically digital camera sensors have a band pass filter to exclude UV and IR frequencies. The band pass filter is often called a hot mirror. \$\endgroup\$
    – Bob Macaroni McStevens
    Oct 22, 2021 at 16:11
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Like the previous answer a lot but if you want the most accurate color you can also buy a color card, something like the X-rite color checker card. Then once you get your images into Lightroom / Photoshop, you can color balance your way back to reality. If you had a scanner you could scan the X-rite color card, and get even closer by using a color picker to pick colors in each, or by comparing histograms. Working in RAW would obviously give you a lot more latitude for transforming the color of the image, without causing software artifacts which are exacerbated by compression.

If you can't afford a RAW workflow just yet, you can maximize the color range you capture by setting your white balance as closely as possible to reality. However setting it accurately is also some amount of guesswork because, unless you are working in the perfect darkness of a studio, you won't know the color of your ambient light sources. You could also get a color meter but that's a hefty investment.

Your cheapest solution would be to get yourself into a RAW capable camera, and get a color card.

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  • \$\begingroup\$ The color checker card is premised on high CRI lighting. Of course if the work is not really color critical, then lower CRI may be good enough. And good enough is good enough. That’s probably really the case here. \$\endgroup\$
    – Bob Macaroni McStevens
    Oct 22, 2021 at 2:25
  • \$\begingroup\$ True, but if he scanned the color card, and his camera-scanner-PSD were all in sync, then the scan of the card will be his true to life reference point. CRI / Light source quality won't matter (except from the standpoint of capturing more dynamic range) \$\endgroup\$
    – Marz
    Oct 23, 2021 at 5:01
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    \$\begingroup\$ I'm not sure how scanning a colour passport is going to aid this workflow. No scan is needed for the workflow, so it's just introducing another random variable. Also, setting white-balance is going to be of zero effect if the light source has 'holes' in it. \$\endgroup\$
    – Tetsujin
    Oct 23, 2021 at 16:37
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Allow me to make a simple list. I will try to explain more later.

Camera, taking the image

  1. Light

  2. Exposition

  3. White balance

  4. Calibration

Processing

  1. Monitor and view conditions

Print

  1. Printer calibration

  2. Material consistency

  3. Manually adjusting variables to the print.

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