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Are there any easily available things I can carry with me, that I probably have already, that I could use as a rough color reference card while taking photos with a phone?

I realize that most phones will heavily process the images themselves, but if I needed to have a way to reference a specific color, it would be helpful if I had something in my pocket that I could add to the photo. For instance, would a clean US $1 bill be useful as a green reference? What else could I add to this to get other colors?

I realize that I could just get a pocket sized color reference card, but that is outside the scope of my current project.

  • why is a color checker passport out of scope again? – Hueco Sep 8 '18 at 1:17
  • @Hueco Probably out of scope because OP doesn't want to buy one. – xiota Sep 8 '18 at 5:45
  • I'm not sure what you mean by "outside the scope of my current project". Do you mean it's too expensive? Generally you can get quite good colour by accurately setting the grey point in your images. Would you consider getting something like a WhiBal or QPcard? – osullic Sep 8 '18 at 9:34
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    US paper money would likely be a poor color reference because the security features, such as special paper, water marks, embedded security strips, reflective ink, and colored markings, change the appearance of the bills when viewed from different angles. Also, previous versions of Photoshop detected when an image contained money and would refuse to load the image. It would be extremely annoying to be unable to edit an image because money was used as a color reference. – xiota Sep 8 '18 at 9:52
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Hum... Let's take the first step.

The most important color reference is white... or should I say gray.

You need to set up your white balance for the light illuminating your scene. You could use a white sheet of paper... but they come in many flavors. Recycled one, super bright, etc. Choose one that has a god whiteness value. The closer to 100 the better one. If it is above 100 it is probably a "fake" white.

But beyond that, no. You are fooling yourself using standard objects. The only reference that they will provide is for that color. A new green bill will be a good reference for a green bill.

Color reference cards are using standardized values so the calibration software assumes what those values should be, so they can correct them using standardized corrections on standardized points on the curves and channels...

Using common objects could be used only for optical corrections, but I would not do that.

  • Since he is using a phone to take pictures, I believe the OP is looking for a reference colour to use in post. So they are unlikely setting white balance for the camera (is there a phone that actually allows you to set white balance?) – Robin Sep 10 '18 at 16:28
  • www.filmicpro.com can set it up for android and io. Besides that you NEED to take a white balance image. You could set the white balance in post using that reference. – Rafael Sep 10 '18 at 17:03
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Apparently, PTFE white matte thread seal tape wrapped around a white polymer eraser works well as a white balance reference. See DIY: Reliable and Cheap Universal White Balance Reference Device.

PTFE tape and polymer eraser

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Likely the Kodak Q-13 Color and grayscale guide will do this trick. Google this and you will see what it looks like. That being said, for your purpose, why not make a reference card using construction paper and school paste. You don't need a calibrated card because you will have the one you made to use as a reference. The Q-13 has been in service for years and years. Their are others, just Google this stuff.

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