What is represented by a histogram in photography?

A histogram in photography is a graphical representation that shows the tonal distribution of an image. It illustrates how tones are distributed across the spectrum of shadows (dark areas), midtones (medium brightness), and highlights (light areas). By analyzing a histogram, a photographer can determine how much of the image falls into each tonal range, which is essential for evaluating exposure.

When a histogram stretches towards the left side, it indicates that there are significant amounts of dark tones or shadows, while a histogram leaning towards the right suggests a predominance of light tones or highlights. A well-balanced histogram will show a more even distribution across the graph, which typically signifies a properly exposed image where details are preserved in both the shadows and highlights.

Understanding this distribution helps photographers make informed decisions about exposure adjustments and post-processing techniques, ensuring that images retain detail and do not suffer from problems like clipping, where important tonal information is lost in either the shadows or highlights.