Hello. I'm new to the forum and don't have a ton of experience shooting digital slrs. I've been cruising through the threads seeing the great macro shots that everyone has been posting and decided to give it a try myself. I bought a Sigma 105 macro Wednesday and have been testing it out over the past couple of evenings.
I purchased locally and I have a few days to exchange it if I'm unhappy. So, my first tests have been to see if i can get a sharp image by setting up something that's not trying to run away from me. I figure I can chase the bugs around later.
After a few tests, I'm a little unsure if I have a good lens. The middle range aperature settings are pretty sharp, and I'm not sure if I should expect any better quality. Wide open seems a little soft, but from what I've read that seems normal for most lenses. My dissapointment in the lens begins around f25 and gets worse as the aperature gets smaller.
I'm focusing manually, using a tripod and remote shutter release as well as using the mirror lock up feature. I know I probably have a ton of room for user error here. I just want to know if I'm expecting too much from this lens or is there something I'm overlooking or doing incorrectly?
On a secondary note: When I close the aperature down and shoot a long exposue, I'm getting artifacts that I've never seen before with my other lenses. I'm assuming this is probably sensor dust, but I can't really figure out why the dots and lint don't show up when shooting with my other lenses, or at wider aperatures?