I have been using the same kit at college since mid September, Nikon D5000 and a Sigma 18-250mm f/3.5-6.3
Now whilst most of my images have been pin sharp and looking good, the past few weeks my lecturer has noticed (and commented at length) that my images haven’t been up to scratch and he knows I can get them sharp because he knows the normal quality of my work.
I haven’t dropped either the camera or the lens. I have never cleaned the censor myself as I’m paranoid I’ll damage it. No one else has been using my gear. I’m at a loss as to what’s causing this, and since I have my final images to shoot soon I am really worried they wont be good enough to pass!
While I’ve been sat here writing this there is only one possible change that I can think of. I have added a UV filter to my lens about a month ago. Could that be it?