Dust and Noise

Two factors that can ruin or greatly reduce image quality are dust and noise. Dust results when hair, debris, and grit, lands on the photo-sensor. Noise, usually seen as pixels not related to the adjacent pixels, arises from the central properties of the photo-sensor of the digital camera or scanner.

You can reduce noise using digital filters only if the noise has a much higher frequency than the picture detail itself -in other words, if the specks are smaller than the image detail. If this isn’t the case, then using a filter will just smudge image information along with the noise signal.

Dust is a serious problem due to the design of SLR cameras, since debris on the photo sensing surface will be recorded on every picture. There is no getting around it, sooner or later all DSLR camera sensors accumulate dust and it will begin showing on your pictures. Dust enters inside the camera body when we change lenses. The digital SLR camera sensor has a static charge and that attracts the dust to it and makes it stay there. Point and shoot digital cameras however do not have to deal with sensor dust issues as the lens is fixed on them. The only way to permanently solve the sensor lens issue and that is to stick with a single lens and never change it. Since that is not a very practical solution and that is not why we purchased a DSLR camera for in the first place, let us discuss how we could reduce the chances of dust entering our DSLR sensor.

  1. Avoid changing lenses in the field if you could help it. It is better to analyze the type of shots you will need to shoot, select a zoom that could do it all and stick with it for the length of the shoot.
  2. If you have access to a car or a room nearby, use it to change your lenses instead of changing it in the open where the chances of dust entering your camera is greater.
  3. Always turn off your camera before changing lenses. As it will help reduce the amount of static electricity in the sensor.
  4. Have your spare lenses ready at hand with back cap removed before you dismount the lens attached to the camera.
  5. Check and clean your lens of dust before attaching it to the camera.
  6. Always clean your front and rear lens caps before attaching those to the lens.
  7. Hold the camera in an upside down position for changing lenses, although it will be hard at first you will soon get used to it.
  8. Always match up the markers on the lens and camera to prevent damage to both lens mount and camera body mount.

In a traditional film based camera, a stray hair will cast it’s shadow at the edge of the frame until it’s dislodged, or a speck of dust will only ruin the frame of film it lands on.

http://enchantingkerala.org/digital-photography-school/how-to-prevent-dust-on-your-dslr-camera-sensor.php