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Color Corrector Question
Can someone explain what the difference is between Gamma, Gain, and Offset within the Color Corrector FX dialog box?
Thanks.
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4 Replies
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output_luminance = (255 * Gain * (input_luminance/255) ^ ( 1 / Gamma ) ) + Offset
The input luminance is rescaled to run from 0 to 1 then taken to the
power of the inverse of the Gamma. This gets scaled linearly by
the gain then multiplied by 255 to go from [0,1] to [0,255].
An offset is then added.If this is too mathy, drop a greyscale ramp test function on the
timeline and apply the color corrector filter to it. Watch the
waveform monitor and mess around with the controls. -
I found this on another forum…
GAIN – handles the overall brightess – but especially at the “top end”, that is, near the whites
OFFSET – handles the “low end” near the blacks
GAMMA – shifts the overall center of your image (brightnesswise) without moving either the “top end whites” or the “low end blacks”.So if your picture is too dark – raise the gain (then adjust the offset a little lower to get decent blacks back)
If your picture is too light, try lowering the gain, and then raise the offset to regain detail in the blacks.
OR – simply “play around” with the gamma to lighten or darken your shotWindows 7 64-bit, ASUS P6X58D, i7 960 3.20GHz, 24.0GB DDR3, 12TB connected storage
http://www.narrowroadmedia.com -
I like this techie explanation. So here my two addons:
– what the heck does the “saturation” slider do then ? Is it the “saturation” from the HSL model, whereby the H & L parts are adjusted in the color wheels ? Or is this YCbCr rather than HSL and it’s the chrominance gain ?
– the tool says something about low/mid/high … what is the definition of whether a given color belongs to the low/mid/high part ?
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Thomas: add a gradient map plugin an set on it low blue, mid green, high red.
This plugins and colors will show in colors what is the luminance range in your clipMárcio Nascimento
– Editor, cinegrafista e fotógrafo –
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