Don't get me wrong, I happen to think that the 2.8 is a superb lens,
unmatched by any non-Leica lens and if it were not so unwieldy I would
probably have thought twice before getting something else. But in my experience
that is what this 3.4 is: something else. I don't really like posts that quote
authorities to back up personal opininions, but in this case you might
like to see what Erwin Puts has to say:
"Leica M TEST REPORTS BY ERWIN PUTS
Apo-Telyt-M 1:3,4/135mm
The 135mm has a special relevance for Leica rangefinder users. Anyone will remember the famous Kruckenhauser pictures of skiers in the snow from the 1930's. The standard of performance had been set by Zeiss with the Sonnar 1:4,0/135, that around 1965 reached its then theoretical optimum. The Leitz version improved even on this and with the new Apo-Telyt 3,4/135 the issue is settled one and for all. This is the lens to have and use on a M6 HM or M3.
Image quality of the 135mm M-lenses
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 of the 4/135 is, even from today's very high standards, outstanding.
Tele-Elmar 4/135
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 slightly 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.
Apo-Telyt 3.4/135
The A-T at full aperture (3,4) the whole image field from center to corners give a high contrast image with extremely fine details very crisply rendered. Stopped done to f/4,0 the A-T improves visibly on the T-E on its ability to render the finest possible details with excellent contrast 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 behavior is excellent, but bokeh aficionados 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 transparency of fine color 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 flawlessly and had no dust or other blemishes
APO-MACRO-Tele-Elmarit 2,8/100.
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.
Compared to the 2.8/135.
At full aperture the center has good contrast and very fine detail is crisply rendered with adequate clarity. In the field the image quality drops visibly and now fine detail is recorded with good contrast. Very fine detail is washed out by softness of edges and low contrast. Stopping down improves somewhat. Generally this lens is miles behind the 3,4/135.
