RustyBug Offline Upload & Sell: On
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Excellent captures ... gotta have that before you can do anything else.
Gamma is the amount of exponential change being applied. A mid tone value of 127 (or .5) with a Gamma of 1.0 remains 127 as .5^1 = .5 (127). Change the gamma to 2.0, and the value of .5 becomes .5^2.0 = .25 (or 64). Similarly a applying a gamma of 2.0 to a value of .9 (230) becomes .9^2.0 = .81 (207).
Depending on which adjustment tool we access in PS, sometimes the program uses the gamma inversely ... meaning that .5 and 2.0 are exponential complements, but the point to realize is that gamma is an exponential adjustment, while other adjustments are linearly applied or multiplication/division to change the numeric values.
Once you understand the mathematical implications of gamma as exponential compared to multiply or levels, then you have the liberty to choose which tool will most effectively garner your intended results and how it will differ from the other tools available.
Gamma really isn't a midrange contrast booster, it is an exponential alteration to ALL VALUES across the entire range.
Taking a value from .1 (25) to .1^2.0 = .01 (2.5) is really crushing down your shadows pretty hard. If you are using gamma for the purpose of midrange contrast boosting, you are generating even more dramatic change in your lower decimal values. If that's what you want, that is fine, but the contrast that is occurring is ranging from the fact that larger decimal values are closer to 1 and thus are less impacted by the exponent being applied as 1 raised to anything is still 1 ... while the lower decimal values are more radically impacted by the exponential change.
This can give increased contrast, but it is not a midrange attribute, it is a gradient attribute throughout the entire range as a byproduct of the decimal math. It may be that we more readily notice when a midrange value changes, but particularly when being used in conjunction with other adjustments, there can be issues with thinking that gamma is oriented to midrange contrast while it can be challenging from some folks to perceive the magnitude of greater change occurring in the lower values and/or lack of change in the upper values.
Gamma can be extremely powerful with the ability to alter the values on magnitude of ^2, ^3 ... and even greater. It also has significant power in the other direction of ^.5, ^.3 and lower. How dramatic or judicious we apply gamma is of course highly subjective, but I find it to be important to know what it is doing throughout your entire range, even if you don't recognize it can be the culprit for blocking up your shadows or flattening your highlights in the process.
Anyway, back to the pic ... took a stab (+1 @ Ben, prefer the raw to work from)
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