What is a Histogram - In Photography Skip to content

What is a Histogram

A histogram is a graph that measures the brightness of an images by representing the frequency of each tone as a value on a bar chart. The horizontal axis moves from pure black on the left side of the histogram, through shadows, midtowns and highlights all the way to the brightest white on the right side. The vertical axis represents the frequency, or intensity, of each tone, with peaks for high frequency and valleys for low. Most digital cameras have both a luminosity histogram (measuring total brightness) and a color histogram (measuring the intensity of red, green, and blue tones).

General Understanding

A histogram is a graphical representation of the tonal values of your images. In other words, it shows the amount of tones of particular brightness found in your photograph ranging from black (0% brightness) to white (100% brightness)

Shadow and Highlight Clipping

Highlight clipping (areas that are completely white and absent detail) occurs if the graph is touching the right side of histogram. Shadow clipping (areas that are completely black and absent detail) occurs if the graph is touching the left side of histogram.

Color Channels

The colorful parts of a histogram is called the channel histogram, which includes three types red, freen and blue. Each type explains the distribution of pixels in this channel.

Underexposure

As you might expect, the camera can’t capture detail throughout the scene. As a result, the sky is overexposed, and part of the foreground are underexposed. This is confirmed by the histogram. Whenever you see a graph that’s cut off on the right side it means there are overexposed (or clipped) highlights.

Overexposure

Many tones are very bright and there are basically no darker tones.  A large portion of the image is blown-out (completely white) and bears no detail at all. As you can see, the histogram confirms that the image is much too bright – it is shifted strongly to the right.

Conclusion

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