:blushing: I feel stupid asking this, but I can't figure out what the problem is unless the lens is broken... It was a beautiful day today so I decided to try out my husband's Sigma lens and get some bird shots in the back yard. First, I do not have experience using a lens larger than a 70-210, and since I chose to use his 70-300zoom macro hand held, I expected the shots to posibbly be blurred from camera shake as I'm not real steady on my feet - But that really wasn't the problem. Getting the thing to focus on something was the problem! I tried it using apeture pri., shutter pri., program mode, and it would not focus on anything clearly. The birds I tried to get were in the tree and I assumed the lens was trying to focus on the branches, but when I tired to focus on the branch by the bird, the lens still wouldn't focus clearly. Naturally, the first thing i double checked, was to see that it was set to normal and not macro mode. I set the camera to manual mode, but what I thought was the focusing ring on the lens wouldn't budge. I looked for a button on the lens and saw only the one for normal & macro. I tried changing focal lengths and tried focusing at 70mm, 100mm, 135mm and 300mm and it would not lock focus on anything! I was about 10 or more feet away from everything I aimed at and the minimum focusing distance of this lens is supposed to be 5 feet! I tried aiming at a bird on the ground thinking the lens was trying to focus on the sky --- it still would not lock focus. I tried using this lens several months ago to photograph a great blue heron which landed at my neighbors duck pond, which is quite a distance away and it didn't focus then either and i thought it was me....maybe it is, but I'm seriously thinking my husband might have dropped this lens at one time [he's broken three others] and thats why it won't focus. The only other thought I had, was perhaps because its a longer focal length and more powerful lens, my unsteadiness is causing the focusing problem.....but I have no problem with my 70-210. The other thing I noticed was my camera battery - the charge was almost gone, but when i put my 35-70 lens back on the camera, the battery listed as being fully charged. Any thoughts? Oh yeah - I'm using a Sony A100. And since the lens would not lock focus there are no photos to post.