Do you have a stuck, dead or hot pixel in your picture from your Canon? Of course you have. All sensors have defect pixels.
Different types of bad pixels
What are dead, stuck and hot pixels? Well, a dead pixel is a pixel that doesn’t receive any power. It will look darker than the pixels around it. Stuck pixels always receive power and will look like a bright pixel. Hot pixels are visible at high ISO, long exposures or if the sensor is warm.
Methods to remove bad pixels
Long exposure noise reduction
Easy but slow. This feature is available from the menu in your camera. It removes defect pixels in raw and in JPEG. You can choose between off, on and auto. When the camera uses Long exposure noise reduction the camera will take a second frame, called dark frame. The shutter speed of the second frame will be the same as for the first frame which means that if you take 1 minute exposure the second frame will also take 1 minute and your camera will be locked during that time.
Increasing ISO
Some camera models from Canon have a built-in hot pixel suppression feature. For example 6D, M5 and R6. At ISO 6400 (6D and M5) or ISO 12800 (R6), hot pixels are removed without any dark frames. The hot pixels left are remainings from hot pixel pairs Canon failed to remove completely. 7D has not that kind of feature.
6D sample raw files with sidecar files for darktable. Don’t use Lightroom, Adobe Camera Raw or other software that can’t turn off demosaicing or the hot pixel filter.
ISO 3200. Notice the pairs of hot pixels.ISO 6400. Almost all hot pixels gone but the remainings of the pairs.
In camera sensor mapping
The inofficial way to remove hot pixels is to do a manual sensor cleaning. If it works for you it will remove defective pixels in raw, JPEG and in video.
Keep the lens cap on the lens and cover the viewfinder. In the menu, start Clean manually and wait for one minute until you turn off the camera. Repeat two or three times if first time doesn’t work.
The green, blue and red pixels below were removed after a sensor cleaning. The singel green one above the cluster was still left after the manual sensor cleaning method.
Raw converter
Easy and fast. This method leaves it to the raw converters to remove defective pixels in raw files. Raw converters like darktable and RawTherapee have a one click module that removes all defective pixels in one strike. Lightroom does it automatically but you can’t increase or decrease the strengh of it. Canon Digital Photo Professional doesn’t remove hot pixels.
Below are two files to try yourself. Canon’s mRAW that already is demosaiced will be hard:
