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Track 2 · Light2 min read

LESSON 10

Reading a histogram

A graph of every tone in the picture, from black to white. It tells the truth when the screen does not.

ONE PICTURE'S TONES · DARK TO LIGHT

A histogram with two humps across the tones and a tall spike pressed against the right edge, where the highlights have clipped.

What the graph shows

From left to right are the tones, from black through the mid-tones to white. The height at each point is how many pixels have that tone, so you can judge the whole picture at a glance.

Dark and bright pictures

A dark picture piles up on the left and a bright one on the right. Neither is wrong: a night street should lean left and snow should lean right. What matters is what happens at the edges.

Clipping

A tall wall pressed against the right edge means highlights clipped to pure white; against the left, shadows crushed to black. A clipped area is one flat tone with no detail in it. Some cameras show red, green and blue graphs as well, because one colour can clip on its own.

A note on RAW

With RAW, the camera's histogram is only an approximation of what the file holds: the picture on the screen is a JPEG preview the camera makes from it.

Try it today

  1. 01Turn on the histogram display and the highlight warning.
  2. 02Shoot a bright window from inside the room.
  3. 03Look for a wall at the right edge and for blinking areas.
  4. 04Dial exposure compensation down until the wall leaves the edge.
  5. 05Compare the two frames.

Figures from Wikipedia, 'Image histogram', 'Clipping (photography)' and 'Raw image format', read 2026.10.16. The steps under Try it today are working practice, not a standard.