On 28 Jan 2001 18:22:12 GMT, clownie@aol.comnospam (Clownie) wrote:

> Is there any kind of "F stop" rating like on SLR lenses? I see that focal
>length number/range for video zoom lenses on the front, but what is that other
>number? It seems to be smaller for smaller lenses...

That other number may be the front mounting thread
diameter, or more likely, the maximum f-stop range,
such as "1.6-2.2:1" or some such (f1.6 at the
zoom short end, f2.2 at the zoom long end - these
are generally "variable aperture" zooms...).
A lens physical size does not determine its maximum
aperture - it is determined by focal length and
clear aperture size, as in FL/aperture-diameter =
f-stop; a very short FL lens with a small diameter
aperture can still be very fast (pass a lot of
light) - there is a common misconception that
lens size or front diameter determines light
passing ability, but this is not (necessarily...)
correct...