Apologies if this is the wrong area for this, but it seemed most appropiate. My friend, a semi-professional photographer recently purchased a Nikon D300, and put his D70 up for sale for $300, with a 28-300mm lens. I figured it'd be the boost in photography I was looking for and so far I've been very satisfied. My issue is this...He told me there's a few specks of dust on the image sensor, but it's only viewable at f/20 and up (according to him). I tried to find the dust by taking pictures of a blank wall with the f/20 settings, and I can't find anything. But now that he's said something I wanna get it off before I realize its where I don't want it to be on a very nice shot. Question is: Can I safely clean this off with some for of light air or something without worrying about screwing stuff up, or should I find a local camera shop and see what they say? I know people who are into photography with SLR's so they may be able to help me, but I wanted a 2nd opinion before I did anything else. Thanks.