Re: [Leica] Apo-Summicron-M 90/2.0 ASPH tested by CDI

["dominique pellissier" <noct@club-internet.fr>]

- ----- Original Message -----
From: Paul Chefurka <Paul_Chefurka@pmc-sierra.com>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Sunday, February 13, 2000 9:31 PM
Subject: RE: [Leica] Apo-Summicron-M 90/2.0 ASPH tested by CDI


> Dominique,
>
> Do you have similar MTF numbers for the old 90/2.0?  From my reading of
> Leica's MTF chart for the APO, the number of 52% you quote is for 40 lp/mm
> at a diameter of 18mm .  At the center the percentage is a a full 10
points
> higher.  According to Erwin (as I understand his comments), the 40 lp/mm
> reading isn't all that significant in general photography anyway - the 20
> lp/mm measurement is of more benefit in predicting the kind of performance
> most photographers will see, especially hand-held.
>
> I'm not sure what you mean when you say "this lens is not an absolute
> winner".  Against what competition are you measuring it?  Are there other
> 90/2.0 lenses out there that are better?  Comparing it to the 180/2.8
hardly
> seems reasonable - they are very different lenses.  Are you saying that
> Leica didn't make it better enough than the old Summicron?
>
> Your comments are confusing - I've got one of these lenses, I've owned the
> 90 Elmarit-M, and the Summicron is significantly better than that lens at
> 2.8, as far as I can tell.  It goes without saying that it's infinitely
> better than the Elmarit at f/2, which is why I bought it.
>
> Paul Chefurka
>
###########
Paul,

I'm not an expert in testing lenses.
In fact if i read mtf tests before buying a lens, it is only in order not to
waste my money, not to split hairs.
For the apo 90 and the old 90 at full aperture, the tests made by CDI give
the same results : good (center), good (edges). So I concluded that the apo
is not an absolute winner.
At 2.8 , the apo gives : very good, good and my elmarit : good, good.The
old summicron : very good, good. So the apo is one more time only equal to
the old summicron and both the summicrons are (slightly) superior to the
elmarit.

I expected something better with the Apo.

BTW,40 lp/mm is the highest filter but my opinion is that a Leica apo lens
must be outstanding as the price is outstanding too.
It seems that CDI uses 40 lp/mm.
But it is possible that 20 lp/mm gives much more contrast for a Leica lens
than for another lens.
Just an  hypothesis.