What's luminance and why doesn't it match RGB average?

Luminance weights green much more (≈72%) than red (≈21%) or blue (≈7%), matching human vision per Rec. 709. A flat RGB average overstates blue and red.

Why does my image look clipped?

If the leftmost bin or rightmost bin is much taller than its neighbours, pixels are bunched at pure black or pure white — detail has been lost. Backing off exposure or contrast before re-exporting usually recovers it.

Image Histogram

Image

Builds a 256-bin histogram for the red, green, blue, and luminance channels (using Rec. 709 weights), then plots them at linear or log scale. Useful for spotting clipping at black or white, evaluating exposure, comparing colour casts between two photos, or checking that a generated image hits the dynamic range you expected. Switch to a single channel to see per-channel statistics (mean, median, min, max).

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How to use

Drop or pick an image (large images are downscaled to 1024px on the long side so analysis stays fast).
Toggle between RGB overlay and individual channels.
Switch to log scale when you have lots of very-bright or very-dark pixels — the tail becomes readable.

Frequently asked questions

What's luminance and why doesn't it match RGB average?: Luminance weights green much more (≈72%) than red (≈21%) or blue (≈7%), matching human vision per Rec. 709. A flat RGB average overstates blue and red.
Why does my image look clipped?: If the leftmost bin or rightmost bin is much taller than its neighbours, pixels are bunched at pure black or pure white — detail has been lost. Backing off exposure or contrast before re-exporting usually recovers it.