Re: brightness vs gamma

beerismygas <beerismygas@xxxxxxxxx> wrote:
: when brightening my photos which were not taken with flash, when should
: i modify (i use photoeditor) brightness and when do i use gamma? they
: seem similar but there must be a good reason for two seperate controls.

: thanks

As I understand the terms Brightness is the adjustment of how intense
White is. This would be like dimming a light bulb. White would still be
white but the intensity of that white is higher. Gamma is more a measure
of how intense the colors are in relation to eachother. So if you want
reds brighter than greens you would adjust more to the red end of the
adjustment (tho the scale may not be labeled as red/green but as a +/-).
So the way I do such adjustments is to first adjust the brightness and
contrast (the range between the brightest and darkest parts of the image),
and then adjust the gamma to tweek for the most asthetic balance of colors
for the particular image. The gamma is also where you will adjust skin
tones so they don't look too red or green (which can occur from varying
lighting or other such conditions at the time of image capture). One other
use for the gamma correction is to make up for the fact that some sensors
are more sensitive to certain colors of light than others. So if you find
that almost all your photos have a reddish cast (even after properly
setting the white balance) you would compensate with the gamma.

If you have experience with older TVs you may have had to play with the
controls and had to adjust the "color" knob. That is Gamma.

Randy

==========
Randy Berbaum
Champaign, IL

.

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