The angle of view is only valid at infinity focus. It gets smaller when you
focus. If you have a lens that focuses t ohalf life size, try it. Get close
to a bookcase or something with the lens at infinity. It's out of focus, but
note the corners of the viewfinder and what is in them. Then rack it fully
out. What was in the corners disappears. The angle of view is getting
narrower.
Actually, the progected immage on the film is getting larger. As the
viewfinder and film size is fixed, less of the circle appears on the film.
Effectively decreasing angle of view.
This is where extension macro has an advantage over internal focussing. Most
IF lenses reduce their focal length and angle of view when going to macro.
Extension works the other way. But you loose light.
Foxy
----- Original Message -----
> G'day
>
> I have noticed in Olympus literature, that the 135/4.5 macro lens has an
> angle of view of 18 degrees, which is the same as a normal 135 tele. The
> other bellows lenses, (20, 38 & 80mm) all have an angle of view of 9
> degrees (at highest magnification). I don't understand this. Can anyone
> explain?
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