Hot, stuck and dead pixels are individual photosites on your camera’s sensor that misbehave. A hot pixel leaks electrical charge and shows as a bright dot in long or warm exposures. A stuck pixel is bright in every photo, even at fast shutter speeds. A dead pixel records nothing and shows as a dark dot. All sensors have a few, they are usually harmless, and most can be hidden by your camera’s pixel mapping feature, by long exposure noise reduction, or with a single click of a spot removal tool.
What is actually going wrong on the sensor
A camera sensor is a grid of millions of tiny light-sensitive sites, one per pixel. During an exposure, each site collects electrical charge in proportion to the light that hits it, and the camera reads that charge as a brightness value. (The how image sensors work guide explains the whole process.)
No photosite is perfect. Even in total darkness, heat causes a small amount of charge to build up on its own. This is called dark current. On almost every photosite it is tiny and fairly uniform across the sensor. A hot pixel is a site with unusually high dark current. It fills up with charge that has nothing to do with light, so it reads as brighter than its neighbours.
Because each photosite sits under a single red, green or blue filter (the Bayer filter), a lone bright site usually turns into a small coloured dot when the camera or editor builds full-colour pixels during demosaicing. That is why hot pixels so often appear as tiny specks of pure red, green or blue rather than white.
Hot, stuck and dead: telling them apart
The three names are used loosely, but the behaviour is distinct, and the behaviour tells you what to do.
- Hot pixel. Bright only in some photos, usually long exposures, high ISO or a warm camera. At a normal shutter speed like 1/250 second it is invisible. It gets brighter the longer the exposure and the warmer the sensor.
- Stuck pixel. Bright, often a fixed colour, in every photo regardless of shutter speed or ISO. It is not leaking charge gradually; it reads a high value all the time.
- Dead pixel. Always dark. It shows as a black or dark dot, visible mainly against bright, even areas like a white wall or pale sky.
There is a fourth case that fools many people: a faulty pixel on the camera’s screen or electronic viewfinder, not the sensor. If the dot stays in the same place on the display whatever you point at, including menus, and never appears when you open the photo on a computer, it is the display. That does not affect your photos at all.
Not dust, not noise
Two other problems produce spots in photos, and they need completely different fixes.
- Hot or stuck pixel: one to a few pixels, sharp edged, most visible in dark areas, unchanged by aperture, and always in the same spot.
- Sensor dust: a soft grey blob many pixels across, most visible in bright plain areas like sky, sharper and darker at small apertures, and in the same spot until the dust moves.
- Noise: fine grain across the whole image, strongest in shadows and flat tones, and in a different random pattern every frame.
Dust sits on the filter in front of the sensor, not on the photosites, so it casts a soft shadow that becomes sharper and darker at f/16 than at f/4. If your spots are fuzzy and grey and appear in a bright sky, see how to clean your camera’s sensor. Noise is a random speckle across the whole image that changes every frame; the individual specks do not repeat. A hot pixel sits in exactly the same place in every photo taken with that camera.
Why heat and long exposures bring them out
Dark current accumulates for as long as the sensor is collecting, and it rises steeply as the sensor warms. That gives you three levers that decide how many hot pixels you see:
- Exposure length. A hot pixel that is invisible at 1/60 second can be obvious at 30 seconds and blazing at several minutes, because it has had hundreds or thousands of times longer to fill with stray charge.
- Temperature. The same camera shows noticeably more hot pixels on a warm summer night than on a cold winter one. The sensor also heats itself: long periods of live view, video recording and back-to-back long exposures all warm it up.
- ISO. Raising ISO amplifies the signal from every photosite, including the stray charge, so hot pixels that were faint become bright.
This is why hot pixels are mostly a night and long exposure problem. You can reduce them in the field by switching off live view between shots, giving the camera a few minutes to cool between long sequences, keeping it out of direct sun before a night shoot, and using the lowest ISO your shot allows.
The lens cap test
You can map every problem pixel on your sensor in ten minutes with no light at all. This test separates hot pixels from stuck ones, and it gives you a reference to compare against later.
- Put the lens cap on. If the camera has an optical viewfinder, cover the eyepiece so no light leaks in.
- Switch to manual mode and RAW. Turn off long exposure noise reduction for this test, since it would hide what you are looking for.
- At base ISO, take three frames: 1/125 second, 1 second and 30 seconds.
- Repeat the 30 second frame at a high ISO you actually use, such as 3200.
- Open the files on a computer, raise the exposure a little if needed, and inspect them at 100 percent magnification, panning across the whole frame.
Reading the results: dots that appear only in the 30 second and high ISO frames are hot pixels, which is normal. Dots that appear even in the 1/125 second frame are stuck pixels. To look for dead pixels, do the opposite: photograph a plain, evenly lit bright surface, such as a white wall, deliberately out of focus, and look for dark points. Record the positions of anything you find so you can tell later whether the count is growing.
A handful of hot pixels in a 30 second exposure is normal for any camera, new or old. Every sensor with millions of sites has some, and sensors gradually pick up new ones over their lifetime.
Pixel mapping: letting the camera hide them
Cameras keep a list of known defective photosites. When one is on the list, the camera ignores its reading and fills that pixel in from its neighbours, which works invisibly because a single pixel is far too small to reveal the substitution. This is called pixel mapping or pixel remapping.
How you trigger it depends on the camera:
- Some cameras run it automatically from time to time, often when powering on or off or during their automatic sensor cleaning routine.
- Some offer it as a menu item, usually named pixel mapping or something similar, found near the sensor cleaning options.
- Some only allow it at a service centre.
Check your manual. If your camera has a manual option, run it with the lens cap on, after the camera has been off for a while and is at room temperature, and do not interrupt it. Then repeat the lens cap test. Most stuck pixels and the brightest hot pixels should be gone. Mapping only hides pixels that are defective at the moment it runs, so run it again if new ones appear.
Long exposure noise reduction and dark frames
Pixel mapping handles the worst offenders. For the many faint hot pixels that appear only in long exposures, the standard tool is dark frame subtraction.
A dark frame is an exposure taken with no light reaching the sensor, at the same length, ISO and temperature as your real photo. It records only the stray charge: the hot pixels and any uneven glow. Subtract it from your photo and those defects cancel out, leaving the real image.
Your camera can do this for you. With long exposure noise reduction turned on, after each long exposure the camera closes the shutter and takes a second exposure of equal length, then subtracts it before saving the file. The advantage is that the dark frame is captured seconds later, at almost exactly the same sensor temperature. The cost is time: a 60 second photo takes about two minutes, and you cannot shoot during the dark frame.
For stacked night sky work, where a gap between frames would break a sequence, photographers usually turn the in-camera feature off and shoot a set of separate dark frames at the end instead, at the same settings and similar temperature, then let stacking software subtract their average. The astrophotography guide covers that workflow.
Removing hot pixels when editing
If a few hot pixels slipped through, removing them is quick:
- Let the RAW processor try first. Many RAW editors silently remove obvious isolated hot pixels while converting the file, so you may see fewer in the editor than in a basic viewer.
- Spot removal or healing. Zoom to 100 percent, set a small brush just larger than the dot, and click it. Pan across the dark areas methodically, in a grid, so you do not miss any.
- Save the work. Hot pixels sit in the same place in every frame from that camera, so once you have healed them on one photo you can copy the spot removal settings to others from the same session.
- Stacking. When you stack several night sky frames and align them on the stars, the stars stay put but the hot pixels land in different places relative to them, so a median or outlier-rejection stack throws them out. Stacks that are not aligned, such as a fixed landscape, will keep them. Moving the camera very slightly between frames (called dithering) makes this work better.
- Star trails. In a star trail blend, hot pixels remain as sharp fixed dots among the curved trails. Remove them from one frame, or subtract a dark frame, before blending.
Avoid treating hot pixels with heavy noise reduction. It softens the whole image to remove a few dots, and strong single-pixel defects often survive anyway.
When it is a real fault
Most pixel problems are cosmetic and fixable. It is worth contacting the manufacturer or a repair service when you see:
- Stuck or dead pixels that survive pixel mapping and show at normal shutter speeds.
- A cluster of bad pixels, or a whole line or column that is bright, dark or discoloured.
- A count that grows quickly from one lens cap test to the next.
- Coloured bands, patterns or random blocks, which point to a sensor or processing fault rather than individual pixels.
If the camera is new or still under warranty, report it early and include your lens cap test files as evidence. A few hot pixels in long exposures will usually be considered normal; stuck pixels in everyday photos after mapping often will not.
Common mistakes
- Cleaning the sensor to remove hot pixels. Fix: check the size and shape. Tiny sharp coloured dots are pixels, not dust, and cleaning will not touch them.
- Assuming a new hot pixel means a broken camera. Fix: run the lens cap test. A few in long exposures is normal.
- Confusing a screen defect with a sensor defect. Fix: open the file on a computer. If the dot is not there, it is the display.
- Leaving live view running between long exposures. Fix: turn the screen off between shots and let the camera cool.
- Using in-camera LENR during a time-lapse or star sequence. Fix: turn it off and shoot separate dark frames at the end.
- Running pixel mapping with the camera warm or light reaching the sensor. Fix: lens cap on, camera at room temperature, and follow the manual.
Try this
Spend 15 minutes making a pixel map of your own camera. Do the lens cap test above at 1/125 second, 1 second, 30 seconds and 30 seconds at high ISO. Open each file at 100 percent and count the dots you can see. Then warm the camera by leaving live view on for ten minutes and repeat just the high ISO 30 second frame. Compare the two counts. You will see directly how much temperature matters, and you will have a baseline to check against in a year. Keep the files in a folder with the date so you can prove whether the problem is growing.
Frequently asked questions
Are hot pixels normal on a new camera?
Yes. Every sensor has some photosites with higher dark current. A few visible dots in a 30 second exposure at high ISO is expected. Stuck pixels in normal daylight photos are not.
Can hot pixels get worse over time?
Sensors do gain occasional new hot pixels over their life. That is one reason pixel mapping exists and can be run again. A rapid increase, or clusters, is worth reporting.
Do hot pixels show up in video?
They can, but video frames are short, so they are much less common than in long stills. When one does appear it stays fixed in place while the scene moves, which makes it easy to spot.
Will long exposure noise reduction remove all hot pixels?
It removes most, because the dark frame records the same defects at the same temperature. Very bright or stuck pixels may still need pixel mapping or a spot removal fix.
Related guides
- How Image Sensors Work: the physics behind photosites and dark current.
- Long Exposure Noise Reduction: how the camera’s dark frame works and when to use it.
- How to Clean Your Camera’s Sensor: for spots that turn out to be dust.
- Noise: the random grain that hot pixels are often confused with.
- Astrophotography: dark frames, stacking and night sky settings.
- How to Use a Tripod: steady technique for the long exposures that reveal hot pixels.
- Night Photography: settings and habits for shooting after dark.