Histogram & Waveform Reader

The four scopes colorists actually use, running on any image you drop in. Switch between an RGB histogram, a luma histogram, a waveform, and an RGB parade, with clipped shadows and highlights measured for you.

Clipped shadows

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Clipped highlights

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Mean luma

Each channel plotted separately. Where all three overlap the image is neutral at that brightness; where one runs past the others, that tone carries a colour cast.

Why scopes beat your eyes

Human vision is relative. Your perception of brightness depends on the surrounding light, the wall behind your monitor, how long you have been looking, and what you looked at before. None of that is stable enough to grade against. A scope measures the actual pixel values, so it tells you the same truth at 9am in a bright room as it does at midnight in a dark one. Professional colour suites are built around scopes for exactly this reason.

Reading each scope

RGB histogram

Three overlaid distributions. Where red, green, and blue align, the image is neutral at that brightness. Where one channel extends past the others at the left edge, your shadows carry that colour.

Luma histogram

A single distribution of perceived brightness using Rec.709 weightings, where green counts for far more than blue. Best for judging exposure without colour confusing the read.

Waveform

Horizontal position on the scope matches horizontal position in the frame. A spike on the right of the waveform means something on the right of your shot is bright. This is the scope for locating a problem, not just detecting it.

RGB parade

Three waveforms side by side. Level the bottoms of the traces to neutralise a shadow cast, level the tops to neutralise a highlight cast. This is the standard way to match two cameras.

Common shapes and what they mean

What you see	What it means
A wall of pixels stacked at the far right	Blown highlights. Those pixels are pure white and hold no recoverable detail.
A wall of pixels stacked at the far left	Crushed blacks. Shadow detail is gone and lifting it will only reveal noise.
A gap at the right end	Nothing in the frame reaches white. The image will look flat and can usually take more gain.
The trace floating above the bottom	A raised black point. Deliberate for a matte look, accidental if you did not put it there.
Blue trace sitting higher than red at the base	A blue cast in the shadows, typical of daylight spill or an incorrect white balance.
Two separated humps	A high-contrast scene such as a backlit subject. Often needs local correction rather than a global move.

A note on clipping

Clipping is not automatically a mistake. A practical light in frame, a specular highlight on metal, or the sun itself will clip in almost any exposure, and trying to save them produces a grey, lifeless image. What matters is whether the clipping is on something the viewer cares about. Clipped skin, a clipped wedding dress, or a clipped sky you intended to keep are problems. The percentages above give you a number to judge against rather than a guess, and anything over a couple of percent is worth a second look.

Frequently asked questions

Is this scope tool free?

Yes. Reading histograms, waveforms, and parades here is free and requires no account. Images are analysed in your browser and never uploaded, so it works on material you cannot send to a third party.

What is the difference between a histogram and a waveform?

A histogram counts how many pixels fall at each brightness level, but throws away where they are in the frame. A waveform keeps horizontal position, so a bright patch on the left of the shot appears on the left of the scope. Use a histogram to judge overall exposure and a waveform to find which part of the image is causing a problem.

What does an RGB parade tell me that a waveform does not?

The parade splits the trace into red, green, and blue side by side. If the bottom of the blue trace sits higher than red and green, your shadows have a blue cast. Comparing the base and top of the three traces is the fastest objective way to identify a cast, because your eye adapts but the scope does not.

Should my histogram always fill the whole range?

No. A low-key night shot should be bunched toward the left and a high-key product shot toward the right. Forcing every image to span the full range flattens the mood you are trying to create. What matters is that you are not losing detail you wanted at either end, which the clipping percentages above measure directly.