luminance of an image

how can i take the luminance of an image in matlab if i have i 256x256 image and i want the luminance of gray scale... what procedure for that can anyone tell me

thnx in advance regards

Answer 1

[Image Analyst]

Use rgb2gray() if you're starting with an RGB image.

[umar siyab]

i know that dear i m talking about the luminance of an image will you get my question?????

[Image Analyst]

Then if you REALLY want luminance (http://en.wikipedia.org/wiki/Luminance) in units of candela per square meter, you're going to have to do a radiometric calibration. Basically make a relationship between your recorded gray level and the "known" luminance from a light emitting source that has been measured with an instrument that measures in candelas per square meter or nits.