How to clean your DSLR or MILC’s image sensor to remove dust spots
It's easy to just grab your camera and go out to take some photos without considering whether the camera is clean or not. Dust on the front of the lens won't normally degrade image quality visibly (unless you have a whole layer of dust on there). But if you have an interchangeable lens camera, dust can get onto the camera's image sensor, where it will cause problems.
Dust on the image sensor shows up as dark blobs in your photos. Unlike film, where the dust would only appear in one frame, then the frame would be wound on, in digital the dust spot will appear in all your photos until it is cleaned off.
Sensor Dust by Brent Schmidt on flickr (licensed CC-BY-SA)
