Just rekindled my interest in photography and new to this foum. I recently bought a secondhand K7, with around 2000 actuations on it. I took lots of snaps since receiving it and at the weekend I noticed a small dot with a small circle around it on all of the images taken with the sky or light background in it. The circle appears around 2 or 3mm in dia when an image is viewed on the computer screen. I went back to the original snaps taken when I received the camera and it appears on those images as well. I have taken the same snap with 2 different lenses and the blemish is still there. Can anyone shed any light on what the problem may be. I have tried contacting the seller but he has not responded yet.......

Thanks