Re: [Leica] optical performance of the tele-elmar 135

[Erwin Puts <imxputs@knoware.nl>]

>My question was : where is the truth ?
>Leica says (but it's normal), Laney says (Leica lens practice, 2nd edition,
>p.188), Eastland says (M-compendium, p.62) that the optical performance of
>the tele-elmar 135 is "recognized as one of the best in the entire Leica
>system".
>The french review "Chasseur d'images" has tested the lens with MTF and
>concluded that the old optical formula(since 1965, no apo-element)gives
>only "good" (3 stars) results. BTH these tests have never been criticized
>by the manufacturers. They are made scientifically as Leica and others do.
>My opinion is that these 2 books (Laney and Eastland)are pure propaganda
>without any ounce of critical vision.
>
>Dominique

Many points here.
"old optical formula". The Planar lens as implemented in the G2 is a
perfect example of this stone age old formula. Almost a one-to-one
correspondence with the original patent.
"No apo": asph and or apo are no guarantee that the optical performance is
stellar. Look at the many Japanese lens companies who in almost every
modern design accumulate floating elements. HD glass, aspherics and then
compare the testresults in Chasseur. You will not find any strong
correlations. BTW apo-elements as such do not exist. Apo is shorthand for
apochromatic correction of a lens. In theory a lens needs to have all
elements of apochromatic correction to be called an apo-lens. But any
manufacturer uses its own definition here.
Manufactures hardly ever comment on testresults. That does not imply they
agree.
MTF testing as such does not imply correct or meaningfull results. Yes
Zeiss and  Leica and many others use MTF tests, differently configured,
with different parameters, different usage of results and different kind of
conclusions.
Your opinion on both authors could be on target though.
Erwin