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isp:imagesignalprocessing [2018/05/29 22:33] – [Automatic white balancing] Igor Yefmov | isp:imagesignalprocessing [2018/06/04 09:13] – Igor Yefmov | ||
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======= Image processing ======= | ======= Image processing ======= | ||
- | + | * [[White balance]], a.k.a. " | |
- | ====== | + | * [[Automatic |
- | ===== What is white color temperature ===== | + | * [[Automatic |
- | A " | + | |
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- | {{: | + | |
- | + | ||
- | When a scene is illuminated by "white" color there' | + | |
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- | For our purposes, we are using individual color channel | + | |
- | ===== Color correction for white temperature ===== | + | |
- | For the calibration purposes we have acquired a Philips "Hue White and Color Ambiance A19 LED Starter Kit" that allowed us to test various illumination scenarios for a range of color temperatures. For a given white color temperature setting we have dialed the red and blue gains to make the scene " | + | |
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- | Corrections to the red channel were way more noticeable than those to the blue one so we approximated the blue gains' graph with a single line, described by the formula '' | + | |
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- | Red channel gains are approximated by two line segments, bordering the '' | + | |
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- | below '' | + | |
- | above '' | + | |
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- | {{: | + | |
- | ==== Experimental data and verification ==== | + | |
- | Here is the table with the results of that testing and corresponding calculated values based on the above formulae: | + | |
- | | ::: ^ Manually set ^^ Calculated | + | |
- | ^ Color, K ^ Red ^ Blue ^ Red ^ Blue ^ | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
- | | '' | + | |
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- | ===== Practical example ===== | + | |
- | What does all that mean in practice? Suppose you have set up your scene with " | + | |
- | + | ||
- | ===== Automatic | + | |
- | ==== Overall idea ==== | + | |
- | ==== Step-by-step algorithm ==== | + | |