Image Color Histogram
View the RGB and luminance histogram of any image to judge exposure, contrast, and color balance.
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Image Color Histogram
A histogram plots how many pixels fall at each brightness level, from black on the left to white on the right. It's the single most useful chart in photography for judging exposure and contrast objectively, instead of trusting a screen that might be too bright or too dim. This viewer draws a separate curve for the red, green, and blue channels, plus an overall luminance line.
Reading it is quick once you know the shape. A bunch of pixels piled against the left edge means crushed shadows (lost detail in the dark areas); piled against the right edge means blown highlights. A well-balanced photo usually spreads across the range without large spikes jammed at either end — though creative images break that rule all the time.
The per-channel view also reveals color casts. If the red curve sits well to the right of the others, the image skews warm; a raised blue curve skews cool. That makes the histogram a fast sanity check before you grade or correct a photo.
How to view an image histogram
- Add your image — drag & drop, paste, or choose a file.
- Read the curves — red, green, and blue channels plus a luminance line.
- Judge the tones — check for clipping in the shadows or highlights.
Tip: watch the edges for clipping
Tall spikes hard against the far left or far right edge usually mean detail has been clipped to pure black or pure white. If you're editing, that's the first thing to pull back — once a channel is clipped, the information there can't be recovered.
Colour histogram: how it works
- What it does
- Plots how an image's pixels are distributed across brightness levels, from black on the left to white on the right.
- Colour output
- A graph with four overlaid curves: separate red, green, and blue channels plus an overall luminance line, each binned into 256 levels.
- How it works
- Every pixel is counted into one of 256 bins per channel. The luminance line uses the standard perceptual weighting (about 0.30 red, 0.59 green, 0.11 blue) because the eye is far more sensitive to green than to blue, so it reflects perceived brightness rather than a flat average.
What you can use it for
- Judging exposure objectively instead of trusting a screen that may be too bright or too dim.
- Spotting clipping — a tall spike jammed against the left edge means crushed shadows, against the right edge means blown highlights.
- Checking contrast by seeing whether tones spread across the range or bunch in the middle.
- Detecting a colour cast: if one channel's curve sits shifted from the others, the image leans warm (red leading) or cool (blue leading).
Tip: Watch the far edges for clipping — once a channel is clipped to pure black or pure white the detail there can't be recovered, so that's the first thing to pull back when editing.
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Frequently asked questions
What does an image histogram show?
It shows how many pixels have each brightness level, per color channel and overall. The left side is dark tones, the right side is bright tones.
How do I read the histogram for exposure?
Pixels bunched on the left suggest underexposure (dark), bunched on the right suggest overexposure (bright). A spread across the range usually means balanced exposure.
What is the luminance line?
It's the combined perceived brightness of all three channels, weighted the way human vision responds to red, green, and blue.
Can a histogram reveal a color cast?
Yes. If one channel's curve is shifted relative to the others, the image leans toward that color — warm if red leads, cool if blue leads.
Where is my image processed?
It happens in your browser, so the result is created on your own device. How any data associated with the tool is handled is described in our privacy policy.
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