----- Original Message ----- From: "Godfrey DiGiorgi" Subject: Re: DA35/2.8 Macro Samples (unofficial)
>> The extra stop of speed is a nice complement to the high ISO >> support. That extra stop gives the >> auto focus a lot more to work with. ... > > If and only if the lens maintains the same or better contrast wide open. > > I found that AF speed and accuracy with the FA20-35/4 was superior to > what I saw with the FA31 Limited ... presumably because the FA20-35 > wide open was more contrasty than the FA31 wide open. Conjecture but > it seemed borne out by other lenses as well. Probably true until the light levels fall low enough that the slower lens just isn't providing enough light for the AF to operate at all. A 1.4 lens has fully two more stops of potential low light ability than a 2.8 lens after the AF has given up for good on trying to focus on anything with the slower lens. Whether this makes any practical difference, I don't know, as I am guilty of conjecture here as well. William Robb -- 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.
