 Image contrast

Image contrast measures how distinguishable image intensities are under a stated definition. For a periodic bright-dark pattern, Michelson contrast is $(I_{\max }-I_{\min })/(I_{\max }+I_{\min })$. For a small feature on a uniform background, a relative difference from that background is often more informative.

A high-contrast image can still have poor spatial resolution, and a finely resolved feature can be difficult to detect if noise masks its intensity difference. Illumination, background, optical blur, detector response and display scaling all affect measured contrast. Choosing a formula should follow the imaging task.