Sometimes, on a digital camera, there are small defects on the digital sensor. They appear as a pixel or two which seem to be either black, colored (hot) or white (stuck). This is ususally not much of a problem, but it can become very annoying.
On my good old Konica-Minolta Dynax 7D camera, I noticed on some of the 2500 photos I shot in Brazil in 2007 that there were a couple of white pixels in the upper third of the picture. This was not too annoying since a white dot on the sky is usually barely visible and easy to correct by most of the smoothing algorithms. And they disappeared any time I cropped down the image for web usage. However, it was clearly visible on some of my best images (those I wanted to keep in full resolution).
This post was first published on Roumazeilles.net in 2007.
Easy to correct did not mean that I wanted to keep that. So, I started to look for software solutions to correct the problem, but it appears that Minolta, Konica-Minolta and Sony digital SLR cameras all share the same approach to hot pixels and stuck pixels. Once a month, when switching off, the SLR camera will shoot a black image (not even opening the shutter) and look for stuck pixels to update the “dead pixel map” of the camera. The switching off appears slower when this happens (the red light will blink a little longer), but after this step the problem is automatically corrected.
If you want to correct it by yourself, the only thing that you have to do is to change the date in the camera menu, move it forward at least further than the next 1st day of the next month, switch off the camera (let it do its little game of red light), switch it on again, shoot one picture, go to the menu and change the date back, then switch off the camera.
After this, your Sony camera updated its hot pixel mapping and knows where to expect them. It will automagically remove them from the picture and just interpolate values from the neighbouring pixels. Instead of having an ugly white spot, you’ll get a microscopic and all-but-invisible loss of resolution (one-pixel resolution loss out of 6 to 20 millions is still acceptable, isn’t it?)
It works with all Sony SLR cameras (and older Minolta or Konica/Minolta cameras). To be kept somewhere in the back of our memory.