Question
What happens when the following settings are changed:
- White balance
- Color tones
- Scene modes
Are these parameters affect the way in which the photo is taken or they are just applied by processing by camera after taking the image?
Or do these parameters change the way the image sensor records the image?
What about changing the contrast, or sharpness?
Answer
The question What's "real" and what's "virtual" on a (digital) camera? has several answers which list the things which are "real" — that is, the things which affect the capture of the RAW image. To crib from the top answers, these things are:
- ISO
- Aperture
- Shutter Speed
- Focus
with some more technical things like image stabilization and mirror lockup as well.
The answers there don't really cover what's "not real", except by elimination, so let me go over your specifics.
White balance and color tones do not affect these "real" things directly — they're applied to the RAW image in in-camera (or out of camera) post processing. However, it's not quite straightforward, since the selected options can affect the metering — a very blue-shifted white balance might cause a different interpretation of what the exposure should be than a very yellow-shifted one. That, in turn, may make the camera's automatic modes choose slightly different settings. But that's a bit esoteric: the straight answer is white balance and color tones are "after effects".
But "scene modes" are somewhat different, since they apply a whole grab-bag of different settings. Some of these, like a fast shutter speed for a sports mode, will almost certainly affect the real image. Others, like portrait modes, may simply chose post-processing options more suited for delicate-appearing skin.
Your last two, contrast and sharpness, are also an "it depends". These things are strongly influenced by the lens you use, your aperture selected, and correct focus. So in that sense, they are real and unalterable. But, local and global contrast can also be boosted in post-production, and usually is — in fact, usually very much so in the default JPEG output from most cameras. Without that, the out-of-camera images would look much more dull and flat than we are accustomed to. A good camera — or RAW processing software — will give you a lot of individual control over these parameters in the post-processing sense.
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