In article <4enoq6$dvt@erinews.ericsson.se>, ebcpecz@ebc.ericsson.se says... (..)

>I have a zoom-lens 28-80mm/f3.5-4.5. What I can understand is that
>the f3.5 is the aperture at the 28mm end and f4.5 is the 80mm. (..)
>If I set the lens at the middle (54mm) do I get f4.0? Is there some >way to know what aperture You get between the ends (is the relation >between aperture and focal length linear)? Does the camera know these >changes when You zoom (I have a Pentax MV)?

Uh, yes, yes, yes, and yes....
Hope This helps