Re: lens brightness

[Martin Trautmann]

On Mon 2001-09-24 (13:32), Ivan Prenosil wrote:
> It can't be (as people sometimes say on this list) as simple as
> lens diameter divided by focal length; otherwise my FA28-70/4
> could not be constant aperture zoom :-)

Constant aperture is done by adjustment 'tricks' of the efficient aperture
- the diaphragm blades can be closed for shorter focal lengths.

In fact I don't know why this should be done. 28-70/3.5-4.0 should be
superior to 28-70/4.0!?

Regards
Martin
-
This message is from the Pentax-Discuss Mail List.  To unsubscribe,
go to http://www.pdml.net and follow the directions. Don't forget to
visit the Pentax Users' Gallery at http://pug.komkon.org .