What’s the difference between hot, stuck, and dead pixels on a camera sensor?
Asked 2/24/2017
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What do hot, stuck, and dead pixels mean on a digital camera’s image sensor? What typically causes each type of pixel defect, and what can be done in-camera or in post-processing to reduce their visibility in photos?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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Excitingly, these terms mean different things to different people. I think the most useful distinction is like this:
- Stuck pixels are always completely bright, as if they're fully overexposed
- Dead pixels are always off, as if receiving no light (these are usually less obvious)
- Hot pixels are not permanently stuck, but show up during long exposures (as the sensor heats up). These usually are defective pixels to some degree, and the same sensor will usually have the same hot pixels in the same conditions.
Some people use "hot" and "stuck" interchangeably, for either one or both of the different situations. I think it's more useful to make a distinction, but be aware that not everyone does — it's most helpful to be a little more verbose and explain what exactly you mean.
"Dark frame subtraction" is an effective way to deal with hot pixels. The same can be done for stuck (or dead) pixels, but generally the thing to do is have them mapped out permanently. Many cameras have a function in the menu to scan for these defects and do the mapping; otherwise, it's usually covered under warranty service. (This may or may not also get some or all of the hot pixels.)
In a digital sensor, all of these usually refer to a single photosite, with its corresponding color filter, so you might have a bright spot of red, green, or blue. This may also "bleed" into nearby pixels during the demosasicing process (but only as an artifact, not from electrical leakage or anything), resulting in + or × patterns.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
9y ago
0
Generated from our catalog & community — verify before relying on it.
These terms are used inconsistently, but a practical distinction is:
- hot pixels: bright pixels that appear under certain conditions, especially long exposures, high ISO, or when the sensor is warm. They may not appear all the time.
- stuck pixels: pixels that consistently read bright, as if fully exposed.
- dead pixels: pixels that consistently read dark or off.
Hot pixels are often related to heat and sensor noise, so they show up more in long exposures and warmer conditions. Stuck and dead pixels are generally persistent hardware defects.
To reduce their effect:
- Use dark-frame subtraction / long-exposure noise reduction for hot pixels.
- Let the camera cool down if heat is contributing.
- Many cameras can do pixel mapping, which identifies bad pixels and compensates for them.
- In post-processing, isolated bad pixels can be removed with healing, clone, or dust-removal tools.
A few bad pixels are not unusual, and dead pixels are often less noticeable than bright ones. Also note that some photographers use “hot” and “stuck” interchangeably, so it helps to describe the behavior rather than rely only on the label.
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AI9y ago
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