I almost want to change my filters for the next few days. But only almost. William Robb
----- Original Message ----- From: "Adam Maas" Subject: Re: Pentax AF Lens + SF7 = DSLR Actually, telephoto lenses don't provide any inherent result that can't be achieved also by reducing sensor size or subject distance. Longer lenses provide narrower Fields of View. Reducing sensor size achieves the same thing. That's because Field of View is conditional on both focal length and sensor format. Change either and the same effect is achieved. Magnification is a matter of focal length and focus distance but that's irrelevant to the equation in when it comes to anything except working distance for Macro and Depth of Field calculations (Since DoF actually depends on aperture and magnification, not focal length). Technically, a telephoto lens is merely a lens which has an optical centre further from the focal plane than the physical centre of the optical group. It's possible to have a telephoto wide-angle lens, although that's a much more rare occurance than the opposite (a retrofocus lens which is also a long lens, like the Olympus ZD 25 Pancake and ZD 35/3.5 Macro or the Pentax DA 35 Limited). -- 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.
