It's definitely time for me to post a new photography tip. Being that I have lots to share on proper camera care and maintenance, I'll just begin today with some simple instructions on how to avoid getting a dirty image sensor on your DSLR (that is, your digital single-lens reflex camera). Digital SLR cameras have removable lenses and this means that dust is able to collect on the sensor.
There are many tips on how to clean your DSLR once it has become dirty (which I hope to cover in the near future), but let's just talk now about how to AVOID your sensor from having this ever happen.
Utilizing these simple tips will help you avoid getting unwanted spots and blotches on your images that come from having a dirty image sensor. (Note: You'll know these spots and blotches are from the result of dust on your camera's image sensor in that they will appear in the exact same spot on all your images).
Here's what I like do to:
TURN IT OFF
Turn off your camera before changing your lens. (Some cameras contain an electric charge that will actually attract dust to it when turned on).
Choose a clean environment when changing lens. (If you are planning to photograph in uncertain weather conditions, pick a lens and stick with it, or choose somewhere safe, preferably indoors, to make the switch).
When changing your lens, hold your camera upside down (the opening will be facing down). This will significantly reduce any chance of dust fall on the sensor while changing the lens.
Have your second lens ready before you make the switch. This will reduce the amount of time your camera is open and sensor is exposed.
If for any reason you do need to remove the lens from your camera for a prolonged period of time, place a dust cap over the lens opening. (Note: Covers can also be attached to the lens itself to keep it clean and away from dust contact).
Photograph a white wall with a large aperture (small number). The results of the image will allow you to easily see whether or not your image sensor is dirty.