The aperture itself varies in diameter as you zoom, the f/stop which is a ratio of diameter to focal length does not. The design of constant aperture zooms is more limited by the diameter of the glass at the tele end. All zooms can be constant aperture zooms if you want to pay for them.
Len --- -----Original Message----- From: Shel Belinkoff [mailto:[EMAIL PROTECTED]] Sent: Tuesday, April 09, 2002 8:34 AM To: [EMAIL PROTECTED] Subject: Re: Using external lightmeter with a Zoom lens... Hi Len, I don't believe you're correct. From what I've seen, the mechanics of variable aperture lenses don't allow that to happen. Could you please explain why the aperture varies over the zoom range when used wide open, but remains constant when stopped down. I'd certainly like to know how this can be. "Paris, Leonard" wrote: > > Yes, I am. > > Len > --- > > -----Original Message----- > From: Shel Belinkoff [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, April 09, 2002 8:13 AM > To: [EMAIL PROTECTED] > Subject: Re: Using external lightmeter with a Zoom lens... > > Are you sure about that? > > "Paris, Leonard" wrote: > > > For example, if you set the aperture at f/8, it will remain at f/8 > > throughout the zoom range. -- Shel Belinkoff mailto:[EMAIL PROTECTED] http://home.earthlink.net/~belinkoff/ http://home.earthlink.net/~belinkoff/darkroom-rentals/index.html - 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 . - 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 .
