If you are using auto-focus, then you may want to have it search from infinity to the front of the lens (Full Range) or you may want the AF engine to work only on finding focus within the immediate neighborhood of the front of the lens (Limit). Presumably if you are manual focusing you won't be trying to find focus across the full range, so you tell the lens you are in MF and it lets you figure out what to do from there.
As Larry said, the Clamp is to lock to achieved focus in place. IIRC, it mechanically brakes movement of the lens elements. stan On Dec 4, 2012, at 9:48 PM, Daniel J. Matyola wrote: > After all the great advice I received from this list on selecting a > Macro lens for my K-r (and future K-5), I made my decision. I decided > to go old school -- and cheap. > > I found a used smc Pentax FA 100mm 1:2-8 Macro for $338 including > shipping. It is certainly well built (and heavy). So far, I've only > played around with it, taking some test images hand-held. So far, It > looks really good. > > The problem: I went online to Pentax to download the manual, but they > no longer carry it. Does anyone know where I can get one. > > The reason I need the manual is the lens has two controls that I don't > really understand. They are visible in the right half of this image: > http://www.photozone.de/images/8Reviews/lenses/pentax_100_28_fa/lens.jpg > . > > From the reviews, I understand that the lens "hunts" a lot in > autofocus mode. The "focus range" control apparently alleviates that > problem, by limiting the rage of focus. I am not clear, however, how > to use the control. Also, why does this control have an "MF" setting, > when manual focus is usually selected on the camera. Is there a > difference between selecting manual focus on the lens rather than on > the camera? > > Even more mysterious -- to me -- is the "clamp" dial. What does this > do, and how? > > Any information or advice will be greatly appreciated. > > TIA, Dan > > Dan Matyola > http://www.pentaxphotogallery.com/danieljmatyola > > -- > 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.
