On Thu, Apr 29, 2010 at 2:40 PM, William Robb <war...@gmail.com> wrote: > > ----- Original Message ----- From: "Adam Maas" > Subject: Re: Macro lens recommendation needed. [Scanned][Spam score:8%] > > >> >> >> In fact the Tamron 90 is somewhat legendary as a portrait lens. But >> the AF on the AF version is so slow as to be useless for anything that >> you can't reliably track in manual focus. Long focus throws are the >> bane of AF performance and a requirement in macros. > > I expect that this is where a focus limiter would be useful. > I just had a look at my A100/2.8 Macro (which is a lens I would not > reccomend to anyone with a DSLR). > The focus throw is almost a full turn from infinity to closest focus, but > from infinity to 1 meter is perhaps 1/10 of that. > You don't get into the long throw part until you are also in the closer than > normal focus range. > I wonder if the Tamron doesn't have a slow gear train. > > William Robb
Focus limiters help alot with prevent the lens from racking back and forth through the entire focus throw, but you still end up with a lens with an unusually long throw even over the limited range which results in pedestrian AF speeds. -Adam -- 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.
