Hi all, I'm sort of new to photography, I mean, I've been into it for about 2 years, but I'm still quite a newbie and there are LOTS of things I don't understand yet. The thing is, I might be buying my first SLR tomorrow (!), I'm buying a used one, since new SLR cameras here cost no less than a thousand dollars and I'm just a student, so... That's not gonna happen. I've been reading online about all the things one should check when buying a used SLR, and I read about checking the sensor to see if it's scratched or anything. The problem is, I have no idea how to do that How do I do this on a Canon EOS 300D? And then, to take a test image when checking for dust, it says you have to set Aperture to f/22, but what if I don't have a lens that can do that? Am I like really screwed? I need help, thanks in advance!