One day, I'm going to do a Youtube video explaining this... the thing is, an F-Stop isn't a fixed size, it depends on the zoom. The kit lens that you have has a maximum aperture size in millimetres. When you zoom in, you're getting less light, so it counts as a higher "F-stop". We say it's a smaller aperture... but it isn't really, it's the same physical size, but because you're getting less light, it LOOKS to the camera like a smaller aperture, so the F-Stop number is bigger.
Was that as clear as mud? Darn confusing, isn't it. Let me try and say the same thing another way...
Imagine you're looking at four lamps on the other side of the room. You zoom in, so now you only see one lamp. You have a quarter of the light, right? The lens should make the aperture larger, to compensate, but with the kit lens, at some point it can't go bigger, it's maxed out. At this point, although the aperture stays at the maximum size in millimetres, it will tell you that the F-Stop is higher, because of the less light you're getting.
F-Stop is a mathematical trick, you see, for the artist in the photographer. It's designed so that a certain F-number means something artistically to the feel of the photo, independent of the zoom. If we started talking about aperture in millimetres, we'd have to ask what the zoom was, to understand how the photo was going to come out.
Topic: Aperture and zoom (Read 266 times)