What a wonderful resource Light Illusion is!

I hate to ask what is probably an amateurish question, but I come across the term "Gamma" so frequently and in so many different instances that I'm quite certain many people are misusing it. Further, I often ask people to define it to which they always reply "it's just the midtones."


Therefore, can anyone please give me a clear and simple definition of what is Gamma? Is it an actual physical thing, or is it just a mathematical equation, algorithm or power law? Also what is actually happening, I mean physically happening, when one adjusts a gamma curve? Or at least point me to a resource that explains it in layman's terms.

Many thanks!


Dezzy

Hi Dezzy,

Thanks for the nice comments

Gamma is simply a value or formula that defines an output change relative to an input...

So, with respect to displays it mean the display output is changed relative to the input, based on a formula.

Charles Poynton's FAQ is a good resource for info: http://www.poynton.com/GammaFAQ.html

The Gamma Curves we refer to here are for use in-camera, so change the image output from the camera compared to the scene being captured.

Cheers, Steve

Thanks, Steve! You explain it so well.

I just got a color monitor today (Asus PA238Q 23") and I adjusted the gamma from 1.8 to 2.2. The 1.8 gamma looked washed out, but not that bad. The 2.2 had much more contrast and saturation.

So if I understand correctly, the monitor (output) is adjusting to my laptop (input) to generate a better image... so why only two choices: 1.8 or 2.2?


dezzy

Changing gamma will not alter saturation (which is effectively gamut) but may appear too due to darker images...

Only having 2 options is normal on low-end displays - 2.2 is PC, 1.8 is (old) Mac.

Steve