High performance ultra wide zooms (UW) dont really exist. Go with a UW prime and even that wont match basic wide primes.
-- J.C. O'Connell (mailto:[email protected]) Join the CD PLAYER & DISC Discussions : http://tech.groups.yahoo.com/group/cdplayers/ http://launch.groups.yahoo.com/group/cdsound/ -----Original Message----- From: [email protected] [mailto:[email protected]] 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 <[email protected]> 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 > [email protected] > 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 [email protected] 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 [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
