How you will measure Gamma and what is gamma correction

[mdueda]

How you will measure Gamma and what is gamma correction

 

[BradtheRad]

Gamma has something to do with narrowing or widening the spread of grey-to-black in an image. It does not pertain to the brighter areas of the image.

If you lighten the gamma, it lightens the darker areas. You can see more detail in those areas.

If you look in the menu of image editing programs, there may be a command to see a histogram. It shows the spread of white to black pixels. It could be a subjective way to measure gamma.

Your computer screen may have a way to change gamma, in the settings menu somewhere.

 

[chuckey]

1. Try wikipedia, := https://en.wikipedia.org/wiki/Gamma_correction
the original problem was that cathode ray tubes used for televisions had a law such that the light coming out of the front was proportional to the voltage drive to the power squared, i.e. double the voltage, four times the light. As the cameras were more or less linear the voltage out varies as light input. Gamma correction was used at the studios to correct for the deficiencies in the CRT (one corrector for 2 million viewers !!). Then colour tubes came along , but the gamma laws held roughly the same. The solid state displays and no one knows what the gamma correction is and how it works. As a professional TV picture grader for 10 years or so, I find that 90% of the SS displays black crush, i.e. there is no detail in the black regions, but this might be because of the limited number of sampling steps in the luminance channel.
Frank

 

[emresel]

Hi;
As chuckey mentioned while taking a picture of smthng with a camera, natural colors and greys are a little bit distorted. This because nonlinear behaviour of capture sensors (and also displays such as tfts). Then you can define a transfer function to compansate it (which is given in the wiki link, the curve on the right hand side at the top). This compansation function is known as gamma correction.
To measure it on TVs and monitors there are some industrial devices called color analyzers.
Hope helps

 

[chuckey]

We used an instrument called a "Grafikon", this was a device through which you peered at the screen and the internal illumination could be altered until the "spot" disappeared. The Black level of the CRT was set up with a "PLUGE" generator. Invented by the BBC - Picture LineUp Generating Equipment*. It gave out a black level video with a 2% pedestal and a negative 2% pedestal, so the brilliance on the monitor was set so one pedestal could be just seen but not the other.
* One wonders how many committee meetings were needed until this name was invented
Frank