Ok, I'm kind of new to photography (other than Point and Shoot) and I'm kind of confused, What does ISO mean and how does it relate to shutter speed (It sounds like it has something to do with it)? Sorry, if that seems stupid to everyone else! Also, Is the F-stop the same as Aperture and how does it effect the depth-of-field to the image? Thanks! PS, I'm using the Nikon D5000 DSLR