Differences between gamma correction and exposure in image processing

Question

Anyone know what is the difference between gamma and exposure? And what is the difference between gamma correction and exposure adjustment in image processing?

Answer 1

Since you don't have an image processing background i would start with a basics

1) Every digital image has a dynamic range of gray levels.Now gray levels are nothing but values which ultimately corresponds to a color. Say Mono-chrome image(Black and white image) has only 2 gray levels i.e. 0 and 1 where 0 means black and 1 means white color. Here the dynamic range is [0-1]. In these images each pixel is stored as a single bit.

Similarly there is Gray-scale images have shades of gray in them. Here each pixel is stored as 8-bit so dynamic range is [0-255]. How? just apply the formula (2^n -1) where n is number of bits. i.e. (2^8 - 1) i.e. 256-1 = 255.

Similarly there are color-images which are 24-bit images.In general the dynamic range of gray levels in image is given by [0 - L-1] where L is number of gray levels.

2) Now once you have understood what is dynamic range lets understand Gamma correction.
Gamma correction is nothing but a function that compress the dynamic range of images so that we can view the image more nicely or properly. But why do we need to compress dynamic range?

A best day to day example is during day time when we cannot see the stars, the reason is because the intensity of sun is so large as compared to the intensity of stars that we cannot see the stars in day time.

Similarly when dynamic range is high in an image then that of the display device we cannot see the image properly. Therefore we can use gamma correction to compress the dynamic range of image

3) Gamma correction can be written as g(x,y) = c * f(x,y) ^ # where # is symbol of gamma (since i don't know how to write gamma symbol here, i have used #) and f(x,y) is original image with high dynamic range, g(x,y) is modified image. C is a positive constant.

4) Exposure as said earlier in an answer its phenomena in camera. I don't know much about it as it is not covered in the syllabus of image processing which i am currently studying.