Miranda

I mainly shoot landscapes so only use 100 or 200 rarely, but the other week I was doing a project for a friend indoors and had to change to 400 because I was using only  available local lighting. The shots did not show any grain, Canon 10D. From the shots in your gallery I can't see why you would use anything else than 100 ISO.

Basically if you you can acheive the shutter speed and / or apperture that you require for the shot use 100 ISO. Only change to 200 or 400 if there is not enough light. Never tried 800 or 1600 but I might have a go at the weekend just to find out.

I'm sure someone here will point you in the right direction on the technical side.

Hope this helps a wee bit.

Steve