Another frequently asked question from our readers is related to dead, hot and stuck pixels they encounter in images or on camera LCD screens. Since there is so much confusion about these different types of pixel defects/malfunctions (people use them interchangeably without understanding the terms), I decided to write a quick article explaining the difference between them to avoid any confusion. Please bear in mind that there is no consensus between photographers when it comes to defining the types of pixel defects. The below information is my way of categorizing defective pixels that you might not agree with.
1) Dead Pixels
A dead pixel is a permanently damaged pixel that does not receive any power, which often results in a black spot on the camera LCD. Since digital camera sensors have color filter arrays, also known as “Bayer filters” in front of them, dead pixels do not normally show up as a black spot, but will rather show up of different color than adjacent pixels, or will be slightly darker than adjacent pixels. A dead pixel is a malfunction that is more or less permanent and does not go away over time. Dead pixels are rare on digital camera LCDs and sensors – manufacturers typically take care of dead pixels during their extensive Quality Assurance (QA) process. Dead pixels might appear on DSLR LCD screens and sensors over time, which is normal.
How to spot dead pixels: dead pixels are easy to spot on the camera LCD. Simply turn on Live View and point your camera at a bright area such as the sky. Dead pixels will always show up in the same spot even if you move the camera. Finding dead pixels on the camera sensor is tougher. Take several pictures with different colors and patterns, then analyze the image at 100% view size. If you see a pixel that shows up in the same spot and changes colors every time, or appears darker than the surrounding pixels, it is most likely a dead pixel.
2) Stuck Pixels
Compared to dead pixels, stuck pixels always receive power, which results in a colored pixel that shows up in the same spot on the camera LCD or on the sensor/images. The colors can be red, green, blue or any combination of these colors. Unlike dead pixels, stuck pixels do not change their color from picture to picture. Stuck pixels are very common, but not permanent like dead pixels – they might disappear overtime.
How to spot stuck pixels: to see if you have stuck pixels, set your camera to Program/Auto or Aperture Priority Mode, then turn on Live View and point the camera around, while carefully looking at the camera LCD. If you notice a pixel that never moves and has the same color no matter where you point your camera to, you might have a stuck pixel on the LCD. To find out if you have a stuck pixel on your camera sensor, take multiple different pictures at a base ISO such as ISO 100 or 200, then analyze the images at 100% on your computer screen. If you have a colored pixel (actually a small cross when viewed closely) that always shows up in the same spot, you have a stuck pixel. It is normal for digital camera sensors and LCDs to have multiple stuck pixels.
3) Hot Pixels
Unlike stuck pixels, hot pixels only show up when the camera sensor gets hot during long exposures or when the ISO is cranked up above 400-800. Hot pixels are very normal and they will show up even on brand new cameras, although manufacturers do their best to map hot pixels out during the QA process. Hot pixels will appear and disappear overtime and if your brand new camera does not have stuck pixels, you can rest assured that you will have them at some point in the future. Every single DSLR camera I have owned and/or used had hot pixels. My Nikon D3s had no visible hot pixels when it was new and now has plenty of hot pixels that are visible in longer exposure/high ISO images. Hot pixels do not occur in LCD screens.
How to spot hot pixels: while keeping the lens cap on, set your camera to Manual mode, turn off Auto ISO and set your ISO to 100 (base ISO). Set camera shutter speed to 5-10 seconds and aperture to a large value like f/16 (to decrease the amount of ambient light that could potentially enter the lens through small holes). Take a picture. Next, set your ISO to 800 and increase the shutter speed to something fast like 1/1000 while keeping the aperture the same. Take another picture. Analyze both images and see if you can spot colored pixels that look like very small crosses when zoomed in. You will probably see more hot pixels in the second photo at higher ISO than on the first one.
4) How to fix dead, stuck and hot pixels
Unfortunately in most cases, you cannot fix dead, stuck or hot pixels yourself. While you might find some online tutorials on how to map out stuck/hot pixels with various software (only works with very old DSLR models), I would not recommend trying those. If you decide to try it out, then do it at your own risk.
So, what do you do with dead/stuck/hot pixels if you have them? If you only have one or two dead pixels on your LCD, don’t worry about them – dead pixels are a normal fact of life. Think of it this way – a typical 3 inch LCD from Nikon contains 920,000 pixels. A single dead pixel means 0.0001% failure rate with 99.9999% of good pixels. Unless you have more than 2-3 dead pixels and they are close to each other, I would not worry about them. Plus, those dead pixels on the camera LCD will never show up in your images anyway! The same goes for stuck pixels on the camera LCD – don’t worry about them unless you have too many.
Now when it comes to the camera sensor, the situation is a little different, because dead/stuck/hot pixels will show up in your images. The probability of having defective pixels on a digital camera sensor is even higher – if you have 920,000 pixels on the camera LCD, you probably have 12+ million pixels on the camera sensor. Dead and stuck pixels are the most annoying ones, because they show up in every single picture. I personally do not care about those, because Lightroom and Photoshop Camera RAW automatically map those out when I import RAW images. If you only shoot JPEG, then it will take a little more time to map those pixels in post-processing, since you have to touch every image. There are some programs out there that will look for pixel patterns and fix JPEG images in batches, so you can more or less automate the process as well. If you see stuck pixels at low ISOs like ISO 100 and 200 and you exclusively shoot in JPEG, then you can send your camera for service to get those pixels remapped. As for hot pixels that show up only at high ISOs and longer exposures – those are very normal to have. Don’t send your camera to manufacturer to remap those, since they will come back in different spots later for sure. Again, if you shoot in RAW, Lightroom/Camera RAW will take care of those.
If you have just bought your camera and you have too many dead/stuck/hot pixels (by too many I define more than 3 on the LCD and more than 5 on the sensor at low ISOs), then send your camera back to the seller you bought the camera from. Depending on the seller, they might issue a full refund or exchange it, or they might charge you a restocking fee. I always buy from B&H and Adorama – they take back products if I am not happy without any questions, as long as I do it within 30 days from the date of purchase.