On 28 Apr 2005 at 0:33, Rob Studdert wrote: > On 27 Apr 2005 at 7:16, Shel Belinkoff wrote: > > > Isn't a macro lens designed for flat field work? If so, wouldn't a regular > > lens used with an extender, a bellows, or helicoil focusing device, be a > > better choice for 3D objects, such as close-ups of flowers or small > > objects? > > Or maybe close-ups of not so small objects? > > Yes, most dedicated macro lenses are flat field corrected. If the primary > point > of interest is in the centre of the frame you might get away with a non-macro > lens pretty easily but the point is that the generally distorted plane of > focus > on the subject side of most non-macro lenses can become a problem at macro > distances. It certainly would be no better for 3D objects, a flat field lens > will generally record any object in close focus with less optical distortion.
To provide an example I just produced a pair of shots at f5.6, one with my A50/1.2 + tube and the next with my A50/2.8 macro lens, nothing changed but the lenses: http://members.ozemail.com.au/~audiob/temp/IMGP2269.jpg 50/1.2 http://members.ozemail.com.au/~audiob/temp/IMGP2270.jpg 50/2.8 Macro Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
