WebcamTest.com
← Back to Diagnostic Tools

Live Histogram

Dynamic Range & Exposure Meter

A live luminance histogram of your feed, updated in real time: what fraction of your image is crushed to pure black, what fraction is blown to pure white, and how much usable range sits between them. This is a direct read of what your sensor is delivering right now, not a lab-instrument "stops" rating — the practical question of whether you are clipping detail, answered honestly.

Camera off

Readout

Live Histogram

  • Crushed Blacks:—
  • Blown Highlights:—
  • Usable Range:—
  • Verdict:—

Share

Share Your Result

Notes

Reading the histogram

Tall spike at the far leftShadow detail being crushed to black. Add fill light or reduce backlight compensation fighting your exposure.
Tall spike at the far rightHighlights blown to white — usually a window, light source, or overexposure in frame. Reposition the light or your camera.
Everything bunched in the middleLow contrast. Not wrong, but flat — increasing the difference between your key light and background usually helps.
Wide, even spread with little at either edgeGood — you are using most of the available range without clipping either end.

Why this is not a "stops" measurement

Sensor dynamic range in photographic stops is measured with a calibrated step chart under controlled, known light — equipment a browser has no access to. What this tool measures instead is exactly what is happening in your current scene, sampled directly from the pixels your camera is delivering. That is a different, more immediately useful question for a video call or stream: not "what is my sensor capable of in ideal conditions" but "is my current setup clipping detail right now."

Benchmark Reference

Verdict Thresholds at a Glance

ResultCrushed / blownFix
GoodBoth under 15%None needed — using the range cleanly.
Shadows blockedCrushed > 15%Add fill light.
Highlights blownBlown > 15%Reduce backlight or exposure.
Clipping both endsBoth > 15%Move the light source out of frame; add fill on the dark side.

These are this tool's own real thresholds, sampled directly from your live histogram.

Step-by-Step

How to Run the Test

  1. Click "Start" and allow camera access when prompted.
  2. Sit in your normal call position under your usual lighting.
  3. Read the live histogram — check for spikes crowding the far left (crushed shadows) or far right (blown highlights).
  4. Adjust one light at a time and watch the histogram reshape in real time.

Common Issues

Troubleshooting & Fixes

Camera access blockedClick the camera icon in your browser's address bar to confirm this site is allowed, or check your OS's camera privacy settings.
Histogram won't stop clipping despite adjustmentsCheck for a bright window or light directly in frame — moving it out of shot is often more effective than compensating with exposure alone.
Result changes a lot as you moveExpected — the histogram reflects your exact current scene, so shifting position relative to your lights changes the reading. Settle into your normal position before judging the result.

Common Questions

Frequently Asked Questions

What does crushed blacks and blown highlights mean?
Crushed blacks means shadow detail has been compressed into pure black with nothing left to recover — you can no longer tell a dark gray from true black. Blown highlights is the same problem at the other end: bright areas clipped to pure white with no texture left. Both are permanent losses of detail in that frame.
Can this measure my camera's actual dynamic range in stops?
No, and it does not claim to. A stops figure needs a calibrated light source and a lab chart, which a browser has no access to. This measures what your current scene is doing right now — how much of it is clipping — which is the practical question almost everyone actually has.
Why would both ends clip at the same time?
That is classic high-contrast lighting — commonly a bright window or light source directly in frame alongside a dimly lit subject. The sensor cannot hold detail at both extremes simultaneously, so it sacrifices one or both. Moving the light source out of frame or adding fill light on the dark side usually fixes it.
How do I fix a flat, low-contrast image?
A narrow histogram bunched in the middle usually means flat, even lighting with no real highlight or shadow — increase the contrast between your key light and the background, or check that backlight compensation is not artificially flattening the image.
Does the histogram update live, or is it a single snapshot?
It updates continuously while the camera is running, so you can adjust lighting and watch the shape change in real time rather than needing to retest after every small change.