Sometimes I line my camera up for a picture but the shutter will not release and I get a little circle icon through the view finder. I quite often find this occurs with close up pictures.
Why is this and how can I get the shutter to work?
In this post
(also posted in the Off-topic forum)you mentioned that you have a Sony A100. My assumption is that your question is related to that camera (you didn't say and you don't have your camera in your "Signature") but going on that assumption I have moved both this thread and the one I just referenced into the Sony forum where you should get the most knowledgeable answers.
I don't have access to an A100 manual here so, sorry, but I can't answer your question.