Color Corrector Question

[Dustin Moore]

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.

[Jeff Schroeder]

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 shot

Windows 7 64-bit, ASUS P6X58D, i7 960 3.20GHz, 24.0GB DDR3, 12TB connected storage
http://www.narrowroadmedia.com

[Thomas Roell]

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 ?

[Márcio Nascimento]

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 clip

Márcio Nascimento
– Editor, cinegrafista e fotógrafo –