Zoom vs Focus

[chris]

Hey guys,

I have somewhat of a "stupid" question here, but please bear with me

When you are focusing on an image, it's my understanding that you are moving the lens closer/farther away from the film surface in order for the light rays to converge on a specific point. When you are changing the zoom setting, are you not also changing the distance between the lens and the film surface (kind of like when you move a projector closer/farther away from the projecing surface)? If this is the case, how can you change the focus without changing the zoom? Shouldnt changing one, automatically affect the other?

Can someone please clarify this mystery for me!

Thanks,

Chris.

[chris]

nobody knows?