I THINK YOU HAVE BEEN "HAD". What you have is a long lens
with a "macro" feature, not a true macro lens. Like I said,
I've read many articles on optical design and true macro
lenses are optimized for closeup magnifications not infinity.
Enlarging lenses are all designed this way for a reason....
Also, I mentioned before that floating element (IF) designs
make it possible to optimize for both near and far distances.
maybe the lens you mention has this type of design?? But even
if it was it probably couldnt compete with a non IF designed
for macro only at it would probably have more elements to get the speed
and IF capability...
JCO
> -----Original Message-----
> From: Rob Studdert [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, September 10, 2002 9:50 PM
> To: [EMAIL PROTECTED]
> Subject: RE: Favourite K mount normal lens poll
>
>
> On 10 Sep 2002 at 20:27, J. C. O'Connell wrote:
>
> > 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...
>
> Yep, lens design sure has moved on since the screw mount era hey?
>
> http://www.cosina.co.jp/sllenses/125.html
>
> http://www.cosina.co.jp/sllenses/spec.html
>
> And for more macro lens MTF graphs see:
>
> http://www.zeiss.de/de/photo/home_e.nsf/3187a822cd4605b7c125670900
> 704e24/8c1f493
> d03703833c12567a80044f090/$FILE/MakroPlanar_2_8_60_e.pdf
>
> http://www.zeiss.de/de/photo/home_e.nsf/3187a822cd4605b7c125670900
> 704e24/f27a4db
> 51c93e9efc12567a80044efea/$FILE/MakroPlanar_2_8_100_e.pdf
>
> Lens resolution is always lost as the magnification is increased.
> it's just the
> law of physics. There is an optimum repro-ratio where the edge
> aberrations are
> lost (due to the magnification of the image circle) however the
> resolution is
> always reduced. Macro lenses most often seem to have better controlled
> chromatic aberrations probably due to their relatively small
> diameter lenses,
> the Lanthar however is a true APO design so the f2.5 speed isn't
> compromising.
>
> The Lanthar kicks most lenses butts (in techo-speak :-)
>
> Cheers,
>
> Rob Studdert
> HURSTVILLE AUSTRALIA
> Tel +61-2-9554-4110
> UTC(GMT) +10 Hours
> [EMAIL PROTECTED]
> http://members.ozemail.com.au/~distudio/publications.html
>
