Re: 100mm/2.8 R APO Macro question

[Eric Welch <ewelch@gp.magick.net>]

Willem-Jan Markerink wrote:
> 
> On 17 Apr 96 at 0:24, Eric Welch wrote about "Re: 100mm/2.8 R APO
> Macro question":
> 
> > Another point on the 100 Apo Macro, that most people have never heard
> > before is that it's a pseudo zoom. The focal length changes as it is
> > focused to it's closest magnification (somewhere in the 90+ mm range to
> > optimize performance closeup). It isn't much of a change, but that will
> > mean that it's not really a 200 mm lens when focused close with the 2x
> > converter. And you can't use it with extension tubes or a bellows. It's
> > a great lens, and I would like to have one, but it has its limitations
> > that need to be taken into consideration.
> >
> > I got that info from the press release announcing the lens and the lens
> > design philosophy behind it. It's still in my files, somewhere.
> 
> There are more macro lenses that do this.
> Actually, all lenses that I've seen so far change their focal lenght
> slightly when focussing. But in the opposite direction: close focus
> results in more tele, instead of less with most macro lenses.
> The pseudo zoom effect you mention can at least be seen in the EOS
> 100mm macro, and the upcoming 180/3.5 macro. I believe the Minolta
> 100mm and Nikon 105mm don't have this pseudo zoom.
> 

On the Apo Macro, it's not an "effect" in the sense that in the case of 
the Leica it's not just changing focus the way all lenses do, it is 
purposely designed to maintain performance by dropping about 8mm in 
focal length as it goes down. Do the other lenses you mention vary that 
much? Must be a basic design principle for macros if that's the case. 
Interesting. Thanks for the info.

> (BTW Roger, were you too impatient to wait for this EOS
> 180/3.5?....shame on you!....;-))

I think the two together would be the ultimate pair. No? <G>
-- 
Eric Welch
Grants Pass, OR