Weber contrast

The Weber contrast is defined as in studies of contrast



\frac{I-I_\mathrm{b}}{I_\mathrm{b}}, $$

with $$I$$ and $$I_\mathrm{b}$$ representing the luminance of the features and the background luminance, respectively. It is commonly used in cases where small features are present on a large uniform background, i.e. the average luminance is approximately equal to the background luminance.