You'd have to give more info. Usually I think transfer function refers to the plot of output gray level versus input gray level, often called "gamma" or the opto-electronic conversion function. Basically it's a curve that usually expands (brightens) dark parts of the photo while compressing brighter parts of the photo. See the Gamma FAQ here:http://www.poynton.com/ Poynton also has a color FAQ here:http://www.poynton.com/ColorFAQ.html for those who are interested. But I've never heard of the gamma being a matrix with 8 unknown parameters. I've heard of it as a 256 by 1 lookup table. The index into the table is the input gray level and the value of the table at that element is the gray level the output image will be mapped to. Go here:http://www.image-engineering.de/ for tools for measuring the gamma of cameras.