I have difficulties in finding the true black carbons in a diamond from an image. Since diamond has a high refractive index of 2.42, it has a critical angle of 24 degrees such that total internal reflection can easily occur (total internal reflection causes fire in diamond) . Now I have taken an image, my main focus is on black carbon. I want to solely find out the true black carbons without those due to total internal reflection. Is there a way to distinguish the difference or filter out the TIR except for looking at the similarities in shape of the black carbons. This looks like an everyday problem but no one really cares its application, please help~~~~ Also I will not consider putting the diamond in an solvent of similar refractive index as diamond. And I know that an image cannot tell all black carbon inside the diamond.