> -----Original Message-----
> From: Rob Studdert [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, September 10, 2002 7:54 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Favourite K mount normal lens poll
>
>
> On 10 Sep 2002 at 16:03, Fred wrote:
>
> > > A50 2.8 MACRO IS NOT A "NORMAL" LENS.
> >
> > > IT WILL NOT PERFORM AT INFINITY AS
> > > WELL AS THE OTHERS LISTED WILL. IT'S
> > > COMPROMISED AT INFINITY FOR BETTER
> > > CLOSEUP PERFORMANCE.
> >
> > I haven't found that to be true, JCO. My A 50/2.8 seems to do quite
> > well at infinity (at least up to a 5 x 7 - 13cm x 18cm - sized
> > print, which is the biggest photo taken near infinity with the
> > 50/2.8 that I can lay my hands on here right now).
>
> I have also found that most macro lenses perform better at
> infinity, in fact
> MTF diagrams for many lenses will bear this out. I have the
> diagrams for some
> CZ lenses and my new APO 125f2.5 Lanthar. The lanthar MTF graphs cover
> infinity, 1m, 1:2 and 1:1 and the results are best at infinity
> and poorest at
> 1:1, this stands to reason as the image circle is being enlarged
> as the lens
> magnification is increased, ie it's moving further from the mount, so all
> errors are magnified.
>
Is the APO 125 f2.5 a true macro lens? If it is and it's performance
is better at infinity than close up something is dreadfully wrong.
If it's not a macro lens, then what you say makes sense...
Like I said before, non floating (non- IF) lenses have to be
optimized at a given reproduction ratio, they are not equal
performance at all subject distances. Seems a little fast to be a true
macro...
JCO
