2 Replies Latest reply on Jun 15, 2010 12:54 AM by undraw

# Uniformity Correction

Are there any uniformity correction feature/API supported on ATI video cards?

Hello all,

I'm a new member here and I just wanted to ask if there are any uniformity correction API's on ATI video cards?

• ###### Uniformity Correction

Hi,

Gamma correction, gamma nonlinearity, gamma encoding, or often simply gamma, is the name of a nonlinear operation used to code and decode luminance or tristimulus values in video or still image systems.[1] Gamma correction is, in the simplest cases, defined by the following power-law expression:

$V_{\text{out}} = {V_{\text{in}}}^{\gamma}$

where the input and output values are non-negative real values, typically in a predetermined range such as 0 to 1. A gamma value $\gamma < 1\,$ is sometimes called an encoding gamma, and the process of encoding with this compressive power-law nonlinearity is called gamma compression; conversely a gamma value $\gamma > 1\,$ is called a decoding gamma and the application of the expansive power-law nonlinearity is called gamma expansion.

Regards.

• ###### Uniformity Correction

Gamma is set in the video card's LUT, however, it cannot compensate for nonuniformity if the monitor would have hardware inconsistencies.

Example: the upper left block of the screen somewhat displays darker than the other blocks... This can be corrected by hardware (by the monitor manufacturer), however, there may still be some inconsistencies and the upper left block would still be darker...

Are there any API's that would adjust all RGB values (possibly inside framebuffer) that would compensate for this nonuniformity in the upper left block of pixels alone?

so that when the monitor receives the framebuffer, it would display higher values for the upper left block, and thus would increase the screen output for the block resulting in a uniform screen luminance...

Thank you very much