Well, that was kind of the point. F/4 is always supposed to be f/4. But if one lens had more losses in the optical path (poor coatings, internal reflections, etc.) it might end up only letting through as much light as a better lens at f/4.5
Personally I very much doubt if any Pentax lens loses anywhere near even 1/3 of a stop in the centre of the image area, let alone there being a noticeable difference between a zoom and a single focal length lens. Where the zoom lens does often perform poorly (especially a fast zoom such as a f/2.8) is in the corners of the frame. Even the acclaimed FA* 80-200/f2.8 shows significant light drop off in the corners when used at f/2.8 (as do the comparable zooms from other manufacturers). On Wed, Jun 28, 2006 at 06:10:15PM -0500, Don Sanderson wrote: > Uh guys, maybe I'm missing something but unless someome is lying > about their product isn't f/4.0 always supposed to be f/4.0?? > It'd pretty much leave slide shooters who use a manual meter SOL > if it wasn't, wouldn't it? > > Don > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of > > Joseph Tainter > > Sent: Tuesday, June 27, 2006 7:38 PM > > To: [email protected] > > Subject: Seen on eBay > > > > > > "A prime 2.8 lens is actually faster than a 2.8 zoom because of the > > increased contrast which you'll find remarkable in comparison to your > > zoom lens." > > > > Got that? > > > > Joe > > > > -- > > PDML Pentax-Discuss Mail List > > [email protected] > > http://pdml.net/mailman/listinfo/pdml_pdml.net > > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
