[Leica] APO_Telyt 3,4/135 report (not for the weak of heart)

[Erwin Puts <imxputs@knoware.nl>]

Testreport APO-Telyt-M 3,4/135

Compared as usual to the predecessors, the Tele-Elmars 4,0/135. The T-E
has an optical layout, consisting of 5 lenses in 3 groups. In comparison
the A-T has also 5 lenses but now in four groups. The T-E is optically
unchanged since 1965 and has been given several facelifts. The optical
performance is, even from today's high standards, outstanding. At full
aperture the whole image field from center to the outermost corners
gives a high contrast image with extremely fine detail crisply rendered.
The subject outlines are sharply delineated and give the image a high
sharpness impression. Stopped down to 5.6 the contrast improves a
little. After f/8,0 the contrast of the very fine object details
diminish a bit. Stopping down further softens the edges of fine detail a
bit more. This performance holds from infinity to 3 meters. Centering is
perfect (I used an older version #2206407), some curvature of field and
a trace of astigmatism can be noted on the bench. This lens is at its
top already at f/4,0 and with stopping down loses a bit of its
impressive performance.

The A-T at full aperture (3,4) the whole image field from center to
cornes give a high contrast image with extremely fine details very
crisply rendered. Stopped doen to f/4,0 the A-T improves visibly on the
T-E on its ability to render the finest possible details with excellent
cntrast and clarity. Stopping down this level of performance holds to
the smallest aperture (22) with only very small losses in edge contrast.

This APO-Telyt shifts the performance level of M-lenses to a higher
platform. It represents current thinking about optical performance as
implemented by Leica. At wider apertures and closer distances the
unsharpness area sets in abruptly and the shapes of objects rapidly lose
its details. For me personally this behaviour is excellent, but bokeh
afficionados might be less happy.

The important characteristic of the A_T is its superior clarity of
exceedingly fine detail that give A-T images a new look. While for some
purposes the T-E gives comparable performance, the A_T excels in a
transparancy of fine colour hues and almost lifelike rendition of very
small subject details. In direct comparison the rendering of the same
fine detail by the T-E is dull, or when going to the edge soft or washed
out. Going one level of detail deeper the T-E produces noise where the
A-T still shines.

This level of optical performance is very sensitive to manufacturing
tolerances. Computer diagrams show the loss of performance when focus
is shifted away from its optimum position.
The lavish and some would say excessive attention to production tolerances
is indeed needed here. My lens worked flawlessy and had no dust or other
blemishes

I also made a sideways comparison to the APO-MACRO-Tele-Elmarit 2,8/100.
Both the A-T and the AMTE are on the same level of performance.
In the far edges the AT is even a bit better. But generally we may now note
that Leica M users are very well served and now can produce images
the envy of the R-users, who had the advantage in the medium telelens field.

The Apo-Telyt is a truly superb lens. It demands users who are willing and
able
to exploit to the fullest their technique and do not hesitate to improve
on their expertise to match the optical qualities of the APO-Telyt.

Erwin