What's the correct term when a photo by exposure or digital post looses colour difference in upper area, bleeding? Over-saturation?


Example at https://www.dpreview.com/reviews/canoneos1d/22 subchapter "sRGB vs. Adobe RGB"

This is NOT a question about Adobe RGB vs sRGB, but the images in the link above very well illustrates colours of the sRGB-images being.. ..oversaturated, cropped, clipped, blown out, distrorted...

The term I'm looking for should, if possible, indicate a lack of quality of the image and NOT an artistic choice.

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    Could you upload a photo with an example of what you're talking about? – Philip Kendall May 22 '17 at 18:01
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    Yup. People is starting to gess what you mean. Probably Caleb is on the right track but... – Rafael May 22 '17 at 19:00
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    It would still be helpful if you could upload an example to make this a clearer question for future visitors. – Philip Kendall May 22 '17 at 19:09
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    This isn't a web forum. Please don't edit the answer into your question (or for that matter provide it as a comment to the question). Instead, mark the answer which helped as accepted, and comment on that answer if necessary. – mattdm May 23 '17 at 10:48
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    "What's the correct term when a photo is over saturated?" Oversaturated? – Michael C May 23 '17 at 17:47

What's the correct term when a photo by exposure or digital post looses colour difference in upper area, bleeding?

  • overexposed means that the sensor (or a significant part of it) recorded too much light for a normal exposure.

  • blown out means that some area or component of the image has maximum values, making it impossible to see any differentiation in that area. Sometimes this is done intentionally, as when the photographer intentionally overexposes the background so much that it becomes completely white. Sometimes it's unintentional, as when a very bright (relative to the subject) overcast sky becomes a boring sea of white.

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Another relevant term is Clipping, see: https://en.wikipedia.org/wiki/Clipping_(photography)

Images exhibiting Clipping will often show areas of solid white, but it can also mean that any specific color channel has been maxed out.

For example, it's not unusual for red features to exhibit channel clipping in daylight shots (primarily seen with flowers and bright red paint).

Over saturated red rose

Here's what the color picker (from paint.net 4.0.16) shows for the color in the center of the marked black box in that image:

Color Palette showing red channel at 255 from paint.net

Note that the red channel is at 255, the maximum value for 8-bit color channel information.

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    I've always wondered, why is red more likely to clip than green or blue? – Mark Ransom May 24 '17 at 19:52
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    @MarkRansom I have read, anecdotally, that it is because of how daylight white-balance is calculated on digital sensors, post-capture. I've noticed that this also happens on film (my sample image on this question is from slide film). Perhaps this would be a good question to ask? – meklarian May 24 '17 at 20:38

In photography, "saturation" means "how colorful a picture is". When you loose color difference because colors cannot be represented by your screen, the color is said to be "out of gamut".

It seems you used "saturation" with another meaning (too much light) in your question, in which case "blown out" is the word you're looking for. Technically, it corresponds to a luminance value greater than the maximum value (e.g. values greater than 255 for 8 bits image formats) and truncating such large values to the maximum allowed value is called "clipping".

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It's unclear from your question, but perhaps you are asking about color quantization (reduction in the color spectrum of an image), also known as posterization.

Posterization example, from Wikimedia Commons
Posterization example, by David Illiff from Wikimedia Commons. CC BY-SA 3.0

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  • Thanks, but the term i was looking for was the unintentional loss of nuances in intense areas of a color, and not an artistic choice. – user247245 May 22 '17 at 19:03
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    @user247245 Posterization isn't usually an artistic choice. It usually happens because colors are "crushed". In a sense, it's a form of lossy compression. Reducing the color spectrum of an image to a fixed palette of, say, 256 colors, results in posterization. – scottbb May 22 '17 at 19:34
  • btw, when an image is posterized, do those colors become out of gamut? – user152435 May 23 '17 at 12:35
  • @user152435 I guess you could say that. I don't know if I would quite put it that way. I'd say the gamut is reduced. If the endpoints of the range of the color spectrum (i.e., 100% red, or blue, or green) weren't changed, then the number of shades transitioning between the endpoints is reduced by qnuatization. So colors in the original before posterization get mapped to the nearest color in the reduced gamut. – scottbb May 23 '17 at 13:47

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