Please: practical advice on colour profiles and histograms

[afre (Alan)]

@RawConvert

@snibgo, curious, how do you yourself adjust exposure?

The how is actually in our discussion. We basically stretch the values to fit the range; e.g., [0…255] for 8 bit images and [0-65535] for 16 bit. So if you have an image that goes from 2-187, the idea is to stretch it to 0-255 or 2-255, depending on what you want to do.

In G’MIC it is as easy as normalize 0,255. In ImageMagick, there are a few options; e.g., -auto-level. To be absolutely clear, this isn’t an exposure adjustment per se because exposure isn’t viewed in this manner; e.g.,

@snibgo

As Carmelo_DrRaw illustrates, multiplying values by a some number has different effects in a linear image compared to an sRGB image. Two stops in linear is a multiplication by four. But the same two stops in sRGB is a multiplication by 1.878, more or less, 4^(1/2.2).

i.e., (2^stops)^(1/gamma), or 2^(stops+(1/gamma)).

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Edit: Made my advice more concise.

@RawConvert

Though this still leaves me (and @Claes ?) wondering how best to proceed.

General advice can only go so far. Different apps have different feature sets. Experiment with each app to see if it meets your needs. Determine what you would like to learn and what your goals are. It may take a while before you have enough knowledge and practice to ask the right questions.

Lastly, I and others in the forum have asked many questions and have had many discussions. It would probably be a good idea to use the search function .