Chris wrote:
Yup. If the lens is on "A" and you're controlling the aperture throughthe
body then it's not an issue. If you're turning the aperture ring, then the
aperture on the body will not match the aperture on the display,and the
display will be correct. The lens will open up to the samediameter at say,
f8, all along its range of focal lengths, but that meansthat the effective
aperture will be smaller at longer lengths. As Iunderstand it (could be
totally out to lunch), constant-aperture zoomsopen up wider as you zoom in
to maintain the same aperture. So f4 at 70mmwill be a physically larger
opening than f4 at 28mm, while a variableaperture zoom will maintain the
same size at all focal lengths. Cheaperto make, but not as much fun. :)chris
I am afraid that this is "out to lunch". Look for example at the
80-320/4.5-5.6 zoom. At 80mm the aperture is 80mm/4.5 = 17.8mm diameter. At
320mm the aperture is 320mm/5.6 = 57.1mm diameter (pretty close to the
filter diameter). AFAIK the variable aperture zoom has the same aperture
mechanism as a constant aperture zoom.
Regards
James Brooks
########################################################################
E-MAILS are susceptible to interference. You should not assume that
the contents originated from the sender or the Zetex Group or that they
have been accurately reproduced from their original form.
Zetex accepts no responsibility for information, errors or omissions in
this e-mail nor for its use or misuse nor for any act committed or
omitted in connection with this communication.
If in doubt, please verify the authenticity with the sender.
Visit us on http://www.zetex.com
########################################################################
-
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 .
