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I have a device with a blue LCD display where the backlight is blue and the letters are white. When I take photos of it with a cheap webcam, you cannot see any letter, because the blue light is too dominant. Does anybody have a cheap solution to this problem?

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    How much control do you have over exposure time/aperture etc? The 'simple' answer is to reduce the amount of light getting in… but that depends on the above. – Tetsujin Sep 26 '20 at 18:13
  • No, I don't have control over exposure time. Would it help to increase the ambient light. Flash light? – Harald Kneidinger Sep 26 '20 at 19:03
  • Try putting a red filter in front of your camera. Orange or yellow or anything that may significantly attenuate the blue. – user10216038 Sep 26 '20 at 21:18
  • @user10216038 The autoexposure routine would probably just increase exposure to compensate. It's going to try and expose the dominant brightness level as mid-tones. Filters only work when there are different colors that can be attenuated differently. – Michael C Sep 27 '20 at 2:38
  • @user10216038 you are right. It worked with both red and yellow cellophane. Sry I cannot upvote. – Harald Kneidinger Sep 27 '20 at 18:25
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Mount a strong yellow filter, the display will image as black and the letters light yellow. If you can find some yellow cellophane X-mass wrapping ribbon or candy wrapping, you can experiment. If you like the effect, then buy a deep yellow photo grade filter. These were common in the black & white era. You can also buy a deep yellow gel filter. These are common in the theatrical stage lighting business. Likely if you look, you can find a piece of yellow flat glass or plastic to test this effect.

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Readabilty issues on LCDs can often be tackled with polarizers without loosing the colour information. You could just hold some cheap polarizer, even a linear, between your webcam and the LCD. Try rotating it up to 90° to find the orientation with the effect you need.

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