What does it mean when color channels clip?

Question

I know about color channels. They represent the amount of color (light) in a photo. Usually in red, blue and yellow or red, blue and green. Black and white only has a greyscale channel.

Setting the white balance kind of calibrates the color channels, correct? I have heard the term clipping color channels used, usually related to white balance. It is apparently something to watch out for. But what does it mean?

At the risk of tooting my own horn, here's an example of a colour channel clipping, and great answers as to its effect. Basically the green color gets saturated, while the other channels kept getting brighter, leading to colour shifts and loss of detail.
https://photo.stackexchange.com/questions/96643/why-is-it-that-when-the-green-channel-clips-it-turns-into-blue — Calyth, Feb 28 '18 at 21:45
Related: https://photo.stackexchange.com/questions/61386/why-does-bright-red-in-direct-sun-come-out-orange/ — OnBreak., Feb 28 '18 at 23:37
Related: Blown out blue/red light making photos look out of focus and How can I photograph bright lights properly? and How to cancel purple stage lighting on subjects? — Michael C, Mar 01 '18 at 09:59

score 4 · Accepted Answer · answered Feb 28 '18 at 19:00

Clipping is a term used when analog data is stored in the digital world. You hear it a lot in audio, but it means the same thing in any field.

Every pixel in an image has data for red green and blue (over simplification alert), and a limited range of values that can be stored. For each color, you can only have a value from 0 to 255. If the actual real-world data over-saturates those values, to data is clipped. For instance, lets say the blue in the image is very blown out. Perhaps it should be a value of 320, but that's too high, so it gets clipped down to 255.

Also, lets say an image is taken with a color balance that is wrong, and you need to adjust the colors. Some colors get brighter and some get darker. If it starts at 205, and you increase the brightness to what would be 280, its going to just stop at 255 and be "clipped". You're losing data at that point.

Clipping has nothing to do with analog vs digital representation of the data. Clipping occurs, when you try to store a real value on a record medium with a limited range (analog or digital does not matter). Film, audio tapes or LP records will also clip, if the signal exceeds the dynamic range of the medium. — jarnbjo, Mar 02 '18 at 15:34

score 1 · Answer 2 · answered Feb 28 '18 at 19:52

Belle, JPhi is correct on the technical representation of color.

In practice, what this means is the ONE channel clips while the other two may be properly exposed - and what THAT means is that you lose detail in the final image for that channel.

A good example is sunset photographs - it's not uncommon to lose detail in reddened clouds because the red channel is overexposed, and hence "clips".

Now, if that is the predominant color in the clouds, then you might see this as a region that has a 'flat' look, with no or muddy detail.

If the area has some mix of color besides red, and only the red channel is clipped, you might still see detail from the other two channels, so in that case you can get away with it.

What does it mean when color channels clip?

2 Answers2