Sensor test
Dead pixel test
Take a photo with the lens cap on and upload it here. We find bright (hot and stuck) pixels, count them and show where they are. The file never leaves your browser.
Photo from the camera
A dark frame is brightened in this preview. The circle colour shows the type, as in the numbers above.
12× zoom, each square is one pixel of the photo.
| # | X | Y | Colour (RGB) | Type |
|---|
How to take the test photo
- Put the lens cap on and cover the viewfinder (the eyepiece cover on the strap, or a piece of tape). A dark room is best.
- Set M mode, manual focus (MF) and base ISO (100 or 200).
- Turn noise reduction off: long exposure NR and high ISO NR. Otherwise the camera removes hot pixels itself and the result looks too good.
- Take two shots: one at 1/60 s and one at 15 to 30 s. Use the best JPG quality, or RAW+JPG.
- Upload the JPG straight from the card, unedited and not sent through a messenger app (they shrink photos).
Dead pixels (always black) only show against a bright background. Take an extra photo of a plain, bright surface (white sky, a wall, a screen showing white) with focus set to infinity at f/8, and upload it the same way. The page detects a bright frame by itself.
What you will find
| Type | What it looks like | Is it a problem |
|---|---|---|
| Hot pixel | A coloured or white dot, mostly on long exposures and when the camera is warm. | A few are normal. Pixel mapping usually hides them. |
| Stuck pixel | Always lit, even at short shutter speeds, usually bright in one colour. | Shows on every photo. Usually it can be mapped out. |
| Dead pixel | Always black. Only visible on a bright photo. | A single one rarely matters, many do. |
One photo cannot tell a hot pixel from a stuck one. Compare a 1/60 s shot with a 30 s shot: a pixel lit on both is stuck.
Limitations
- RAW. A browser cannot read raw sensor data. From a RAW file we take the JPG preview stored inside it. The camera has already processed it (noise reduction, sometimes a lower resolution), so a JPG gives a more reliable result.
- Noise reduction and pixel mapping. The camera can hide faulty pixels in its JPGs. Good for your photos, but the test will then show fewer than the sensor really has.
- Temperature and exposure. Hot pixels multiply with long exposures, high ISO and a warm camera (for example after shooting video).
- JPG compression blurs very faint dots, so the faintest ones may be missed.
- HEIC/HIF opens only in Safari. In other browsers, switch the camera to JPG.
- This tests the sensor, not the camera screen. Dead pixels on the screen are visible by eye on a plain background.
Buying a used camera? Check the shutter count too, and read what else to look at.