On Fri, 26 Jan 2001, Bill D. Casselberry wrote:
> > > angle 84-27 degrees
>
> > So in other words it covers 9mm less than they say it does??? If this
> > covers 27mm, what does a 28mm lens cover? How about the FA* 24/2?
>
> Not to Worry, Chris. These are angle of view numbers, in degrees
> of arc - not focal length in mm's. At the wide end you get near
> to 90degree field of view and at the tele end about 1/3rd as much.
Let's see if I'm thinking straight...
At infinity, it is
f = d / (2 * tan(a/2))
where f: focal lenght, a: angle of view, d: diagonal of the film size,
43mm in our case.
So, the real focal lenght of this lens is, in the short end:
f = 43mm / (2 * tan(84/2)) = 23.88mm
and at the long end:
f = 43mm / (2 * tan (27/2)) = 89.55mm
Well within the usual margins.
j
--
-------------------------------------------------------------------------
Juan J. Buhler | FX Animator @ PDI | http://www.crosswinds.net/~jbuhler
-------------------------------------------------------------------------
-
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.
