> 
> From: Kostas Kavoussanakis <[EMAIL PROTECTED]>
> Date: 2005/09/06 Tue AM 08:57:10 GMT
> To: pentax-discuss@pdml.net
> Subject: Re: Film Lenses on Digital
> 
> On Mon, 5 Sep 2005, Godfrey DiGiorgi wrote:
> 
> > A D-FA50 macro lens is designed to be best at flat-field imaging, stopped 
> > down to f/8-f/32, in the near-focusing range. An A50/1.4 is designed for 
> > general pictorial use at wide apertures, and will not perform at its best 
> > at 
> > copystand distances.
> 
> It was either in the general Pentax lenses and accessories booklet or 
> the manual of the 1.7x AF T/C that I read that the 50/1.7 is 
> recommended for macro work with extension tubes; the 1.4 was 
> recommended against.

IIRC, that was deduced to be due to the flatness (or lack of) of the focus 
plane.

m


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