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There's a room with windows closed by curtains, it's night outside and the only light source is a set of LED filament lamps inside the room. Lamps are designed to have 2200K color temperature to have "retro" look and so light is notably yellowish and all the scene lit by these lamps also looks yellowish to an eye.

Then there's a point-and-shoot digital camera with "scene modes" like "sports", "sunset", "landscape" and the like. Camera can only produce JPEG, so all post-processing is done inside the camera.

Camera positioning and focal length is the same during all filming so camera sees the same scene all the time.

In "landscape" mode the resulting shot is not yellowish — it looks as if it was lit by a 4000K-6500K color temperature fluorescent lamp. In "sunset" mode the shot looks yellowish more or less the same as what an eye sees.

So post-processing behaves differently. It deliberately changes colors in "landscape" code. Why would it do so?

It's not something like automatic exposure where a camera cannot know the expected brightness of an object and so guesses how bright is should look. If the camera doesn't do that we would have to either manually set exposure or have a ton of severely overexposed or underexposed shots.

Visible color of an object looks like something objective — if it looks yellow then it looks yellow, why change it in the first place? I just don't see how this color alteration is useful.

Why does a camera alter the colors in the entire scene during post-processing?

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    Possible duplicate of What does an unprocessed RAW file look like? – xiota Mar 13 at 18:25
  • @xiota That's a related question but certainly not a duplicate. My problem is "why does the camera produce some weird effect", yes, that can be answered by explaining raw. – sharptooth Mar 14 at 8:21
  • What "weird effect"? What you describe is normal camera behavior. You can turn it off by picking one of the white balance presets. – xiota Mar 14 at 8:28
  • It's weird to me because I don't expect it. It's normal to you because you expect it. The camera is not broken but I can't figure it out that's why I asked the question. – sharptooth Mar 14 at 8:31
  • If you don’t want the camera software to make editing decisions for you then shoot in raw and control all of the decision-making in post processing. – Alaska Man Mar 14 at 17:41
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Visible color of an object looks like something objective — if it looks yellow then it looks yellow, why change it in the first place? I just don't see how this color alteration is useful.

This is the fundamental misunderstanding. Visible color is not objective at all. That sounds surprising if you haven't really stopped to consider or investigate, but it really is the case. Remember the blue/yellow dress?

the dress

"Color" is actually a sensation that arises in the mind, not a physical property. Unlike, say, scent, which relies on specialized receptor neurons for each smell, color is largely the result of complex subconscious processing in the brain. Our color perception is very dependent on situation. (In more depth, see this answer to a different question).

So, that's the first thing. The camera can't just show you "true color", because it's just a dumb mechanical device. In some ways, the post-processing it does to create a JPEG mimics human color perception (because, hey, these cameras are made for humans), but fundamentally a lot of decisions are up in the air. This is why white balance is a user-selectable parameter even on the most primitive digital cameras, and on the ones where just about everything else is always automatic.

Related to this, then, is the matter of taste in processing for different subjects. For example, it's usually the case that when photographing people, we want to mute color a bit to downplay skin blemishes. And for landscapes, people often want pushed up colors to make greenery or fall foliage or rock formations or whatever stand out.

Your camera's scene modes are black boxes — you can't see what affect they actually have, beyond guessing from the name and the manufacturer's description. But they definitely do guide the camera's choice in color processing. It sounds like in your case, it also affects the camera's assumptions about white balance (which is fairly reasonable, as a landscape is not normally lit by candles).

If you're not happy with that, it's best to avoid scene modes. The ultimate version of this, of course, is shooting in RAW. You note that your camera can't do this, so it may just have to be a limitation you must accept for — but something to consider for now next time you get a camera.

See also Are scene modes, white balance, color tones, and similar just post-processing effects?

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    Nice animation... but you reminded me that ugly photo of the dress debate... – Rafael Mar 13 at 20:46
  • @Rafael I know, but it's really the most dramatic and universal example I can think of. – mattdm Mar 13 at 21:13
  • Would it fair to say that the camera sees the entire scene and has to decide how it would need to produce a JPEG such that it "looks reasonable" and the "scene mode" is used as a hint? – sharptooth Mar 14 at 8:23
  • @sharptooth Yes, that's fair (as long as you remember that "sees" is not in the same sense as human seeing something, and "decides" means "uses a relatively primitive decision-tree" rather than "uses judgment"). – mattdm Mar 14 at 21:16
  • ...and in some cases it might be less about "reasonable" and more about "wow factor". ;) – junkyardsparkle Mar 14 at 21:17
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It's the effect of changing the white balance that you are seeing in the color shift of the different modes. The camera has to guess the white point of the image in order to render the JPG in automatic mode. In the Landscape mode it is guessing you are outside under natural light. In Sunset mode it guesses the light is yellow at sunset and renders the colors accordingly.

The white point is the RGB values that define what our eyes see as white. But the camera can only capture what its sensor sees, so it doesn't know how we perceive white in the scene. It makes its best guess as to what is white instead.

This is one reason photographers use RAW -- you can change the white balance to whatever you like in post processing. If you have the camera process the RAW image itself to produce a JPG, it has to guess the white balance.

Check your camera to see if there is a white balance setting you can control. You may be able to manually set white balance to get the colors you want.

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Why does a camera alter the colors in the entire scene during post-processing?

Everyone with normal color vision requires the camera to process images to see something reasonable. If the camera did not process the colors, images would look something like this (see What does an unprocessed RAW file look like?):

unprocessed raw

If you feel you do not need the camera to process images the way everyone else expects it to, you can do as Alaska man suggests:

If you don’t want the camera software to make editing decisions for you then shoot in raw and control all of the decision-making in post processing.

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