a 12mm lens on APS is not as wide as a 15mm lens on FF hence, the A15mm wont perform as well on on FF or even APS as a 12mm on APS. (in general). The problem is that it takes to many elements which hurts the flaring reduction. Cost and lens speed are also factors. I would bet the DA 15mm outperforms the A15 on APS as the DA15 isnt designed to cover FF like the A15 is so it can be tweeked for Aps.
-- J.C. O'Connell (mailto:hifis...@gate.net) Join the CD PLAYER & DISC Discussions : http://tech.groups.yahoo.com/group/cdplayers/ http://launch.groups.yahoo.com/group/cdsound/ -----Original Message----- From: pdml-boun...@pdml.net [mailto:pdml-boun...@pdml.net] On Behalf Of P N Stenquist Sent: Monday, April 12, 2010 3:52 PM To: Pentax-Discuss Mail List Subject: Re: Ultra-wide zooms On Apr 12, 2010, at 3:38 PM, J.C. O'Connell wrote: > High performance ultra wide zooms (UW) don't really exist. Go with a > UW > prime > and even that wont match basic wide primes. > > -- The DA 12-24/4 is reportedly comparable in performance to the DA 14/2.8, although it's a stop slower. I've also read that it's actually better than the A 15/3.5 at comparable FOV. I haven't compared it directly to either, but I know from experience that it's an excellent lens, capable of generating a nice, crisp double page spread at 12mm. Good tool. Paul > J.C. O'Connell (mailto:hifis...@gate.net) > Join the CD PLAYER & DISC Discussions : > http://tech.groups.yahoo.com/group/cdplayers/ > http://launch.groups.yahoo.com/group/cdsound/ > > > -----Original Message----- > From: pdml-boun...@pdml.net [mailto:pdml-boun...@pdml.net] On Behalf > Of > David Parsons > Sent: Monday, April 12, 2010 3:12 PM > To: Pentax-Discuss Mail List > Subject: Re: Ultra-wide zooms > > > There are two common crops for dSLRs as compared to FF SLR, 1.5 > (Nikon and > Pentax) and 1.6 (Canon). > > Canon has a 1.3 crop on some of their pro bodies. > > P&S sensors are a whole other barrel of fish and there are many > sizes, but > they don't correlate because the lenses are not interchangeable. > > On Mon, Apr 12, 2010 at 3:00 PM, Keith Whaley <keit...@dslextreme.com> > wrote: >> P N Stenquist wrote: >>> >>> On Apr 12, 2010, at 8:48 AM, Keith Whaley wrote: >>> >>>> Bong Manayon wrote: >>>>> >>>>> Thinking of ... >>>>> 1. Pentax DA 12-24 >>>>> 2. Sigma 10-20 >>>>> 3. Tamron 10-24 >>>>> Am not into fish-eyes so those options are out. Any votes for or >>>>> against any of those listed above? Thanks! >>>>> Bong >> >>>> I don't think those focal lengths are 35mm-equivalent numbers. I >>>> suspect they're double ~ such as the Pentax DA 12-24 is really like >>>> a 35mm lens of 24-48mm focal length. Nice wide angle-to-normal >>>> lens, >>>> but hardly a fish-eye... >> >>> First, the conversion factor for angle of view is 1.5. >> >> Was Bong talking about a specific camera? I know we were talking >> digitals, but, I thought each camera had it's own conversion camera. >> In my limited experience, which does NOT include DSLRs, most cameras >> differ a little as to what their 35mm equivalent is. I avoid the >> uncertainty by referring to the owner's manual for each camera. They >> always mention it... >> >>> So the 12-24 has the same _angle of view_ on an APS-C DSLR as an >>> 18-36 would have on a conventional 35 mm frame. >> >> Cropping factor, or what I call the telephoto effect, brought on by >> the size of the sensor. In other words, the ratio derives from how >> much smaller the DSLR's sensor is compared to 35mm film size. >> See: >> >> http://www.minasi.com/photos/dslrmag/ >> >>> However, the focal length is 12-24. That doesn't change, regardless >>> of the format. Furthermore, it's not a fisheye on any format. It's a >>> rectilinear lens. In other words, the optics make the verticals as >>> true as possible given the size of the elements and the constraints >>> of physical science. Paul >> >> Quite so. Thanks Paul. >> >> keith whaley >> >> >> -- >> PDML Pentax-Discuss Mail List >> PDML@pdml.net >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above >> and >> follow the directions. >> > > > > -- > Aloha Photographer Photoblog > http://alohaphotog.blogspot.com/ > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above > and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
