Image Histogram
Image Histogram - a browser-based image tools utility.
Browser tool
About Image Histogram
A histogram shows how many pixels sit at each brightness level, which is the surest way to tell whether a photo is correctly exposed, flat, or has lost detail at one end. It answers a question your eyes cannot, because a screen at the wrong brightness lies to you. Reading the histogram is free and happens online. The photo is measured without uploading it, no watermark is written anywhere, and you need neither an account nor a sign up to look.
How to use it
- Open a photoThe channels are computed in the page from the decoded image, so nothing is uploaded.
- Read the shape, not the heightThere is no correct histogram shape. What matters is whether the data runs off either edge, which is where detail has been lost.
- Compare channelsRed, green and blue plotted separately show a colour cast that the combined luminance curve hides completely.
Clipping, and why it cannot be undone
When the curve piles up against the left or right edge, pixels have been recorded as pure black or pure white. Those pixels hold no detail to recover — every one of them is the same value — which is why an over-exposed sky stays blank however far you pull the exposure slider down.
What it does not do
- A histogram describes the file, not the scene. A deliberately dark photograph has a left-weighted histogram and is not wrong.
- This reads the decoded image. A raw file processed by a camera or an editor has already had a curve applied, so the histogram reflects that processing rather than what the sensor captured.
Questions people ask
- What should a good histogram look like?
- There is no single answer, which is the most useful thing to know about them. A high-key portrait and a night scene have opposite shapes and both can be correct. Look for data running off an edge, not for a particular silhouette.
- Why do the colour channels look different from each other?
- Because the scene, or the lighting, favours one. A strong separation usually means a colour cast — tungsten light pushing red, shade pushing blue — and correcting white balance brings them back together.
Questions about ToolsVerse itself — privacy, cost, what happens to your files — are answered in the frequently asked questions.
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