Dirty Sensor
One of the advantages of the SLR is the great range of lenses that are available. Whether you prefer a fixed focal length (“Prime”) lens or a variable focal length (“Zoom”) lens, your camera manufacturer will have them available in various sizes and qualities, and to complicate your choices, for most of the common brands of camera, there are lenses available from other manufacturers as well. Inevitably, you land up with several different lenses for your camera (many, if you are a lens freak), and before setting out on a shoot you put the most likely one onto your camera body, and one or two alternatives into the camera bag or one of the pockets of your super safari jacket with all the pockets.
And so we come to one of the disadvantages of the SLR – they attract dirt and dust. Between the time you remove one lens and mount the replacement, every dust particle within a 20m radius will have woken up and started charging for the opening of your camera body, and the next time you take a shot the dust particles that made it will take advantage of the raised mirror to settle on the sensor.
What can you do? You can minimise the time in which dust can enter by changing lenses as quickly as possible. You can reduce the attractiveness of your camera for dust by turning it off before removing a lens. And, when changing, you can stand with your back to the wind, so that dust isn’t blown in, and the dust that is attracted has to work harder to get to the camera.
Great advice Austin. Dust really is a problem. If I want to change lenses indoors I turn off the camera, leave it on a flat surface, put the new lens beside it, then switch the lenses as quickly as possible, making sure to replace the cover on the old one. If I am outdoors I try to get as much shelter as possible, in a car or behind a wall or even using the camera bag as shelter. I still need to get the sensor cleaned professionally every now and again.