Many of these camera have some sort of device to actually help to clean your sensor when you switch them on. Sort of like vibrate the sensor to shake off any dust, but that will only go so far if you've only got little dots of dust on your sensor.
So how do you know whether or not you need to get your sensor cleaned. You can get your sensor clean dirt from many places such as camera stores but I tend to make sure that I go to a reputable one to do that.
You can get your own sensor cleaning kits, although I've never used any of those myself to actually clear the dirt off. I prefer the idea of taking it to someone. Also be a little bit careful when you're changing lenses too. Make sure you're not in a dusty area. I tend to hold the camera down a bit to kind of stop dust getting in, because if I'm obviously doing it facing up then dust could fall on it. But quite honestly, they can't really be helped very much.
one way you can check out your sensor is to actually just get a piece of white paper. Make sure you've got it fairly evenly lit as evenly as possible. Prop it up somewhere and you probably will need to focus manually on this. Zoom right in and set your camera to a very high f-stop so you've got a very small aperture (like f-22).
Take a picture of the white paper, and then move it a little to the side and take another picture. By that way, if you do see a dot on there, in the same place even after you moved the angle of your camera then you know that there is something that is posibly on the sensor. You can do it too if you're outside with nice clear blue sky.
Just take a picture of the sky. Remember, don't point it at the sun, just onto a plain bit of sky.
So now that you've taken your photograph, what you want to do is get it onto your computer to check it. It doesn't matter whether it's windows or Mac, just open it up in some picture editor. What you want to do is zoom in and by that way you'll be able to see better what's goin on.
So you just zoom in and then scan around to see if there is any spot, if that spot appear on the same place at the second picture you take, then it means that you have dust on your sensor.
Taking it and getting it cleaned is a good idea. You're welcome to have a go yourself although i recommend getting someone professional and getting it cleaned.
