§ 11 — Tools / 18Photo files● Runs in your browser
Histogram and clipping checker
Open a photo to see its luminance and RGB histograms and highlight clipped shadows and highlights, all processed in your browser.
All toolsChoose a photo to draw its histogram and check for clipping.
How it works
The method behind the numbers.
A histogram counts how many pixels sit at each of the 256 brightness levels, dark on the left and bright on the right. Pile-ups against either edge mean detail has been lost there: shadows pushed to pure black, or highlights blown to pure white.
Y = 0.2126 R + 0.7152 G + 0.0722 B (Rec. 709 weights)
clipped shadows = pixels with Y = 0
clipped highlights = pixels with Y = 255- The weights are applied to the 8-bit values as stored, without converting to linear light first. That is a common approximation, not a colorimetric measurement.
- The photo is shrunk to about 512 px on its long edge before counting, so the percentages are close but not exact. Shrinking blends neighbours, which can hide a few isolated clipped pixels.
- This reads the exported file you open, in the colour space the browser shows. It is not the raw sensor data, and an in-camera histogram may differ.
- The clipping overlay paints highlights red and shadows blue, using the same luminance test as the percentages. “Any channel” in the highlights note counts pixels where red, green or blue alone reached 255, which can clip colour detail before luminance does.
- The median is the level that half of the pixels fall at or below; the mean is the average level.