[Leica] Summicron 28 part 2

[imx <imxputs@knoware.nl>]

The performance.
At full aperture this lens exhibits a  high contrast with crisp definition
of exceedingly fine detail over most of the image field, softening in the
field from image height of 9mm. A faint trace of astigmatism and field
curvature can be detected. Stopping down to 2.8 improves the center area
(diameter 12mm) and also brings in a higher microcontrast in the outer
zones. Corners however lag a bit and stay soft with a limited definition of
coarse detail.  Stopped down to 4, contrast becomes very high and the
optimum is reached with a very even performance over the whole image area,
excepting the extreme corners. At 5.6 we se a small drop in microcontrast of
the fine textures and from 8, the overall contrast drops a bit. We have to
put this in perspective, of course as we relate it to the optimum aperture.
At 5.6 and smaller, the Elmarit-M 2.8/28 is a bit behind the new Summicron
28. 
Distortion is about the same as with the Elmarit 28mm and vignetting is
just visible with with 2 stops in the corners at full aperture, about the
same as the Elmarit at 1:2.8. In general use, this falloff can be neglected:
even on slide film one has some difficulty noticing the darkening of the
extreme corners. 
Close up performance at 0.7 meters and full aperture shows excellent
performance with high contrast rendition of very fine detail.
Flare is very well suppressed. Of course: you can construct situations where
secondary images and veiling glare is quite visible, but even here the
images retain contrast and some saturation. A lens shade is needed, when the
light sources may shine in or close to the front lens. I will give this
topic a separate treatment. Leica has redesigned the  front part of the lens
where the shade is attached for easier handling. All wide angle lenses
suffer the same problems here. It is a tribute to the design team that they
have given this topic additional attention.
The comparison.
The Elmarit 28 at 1:2.8 is slightly behind the Summicron at 1:2,
specifically in the contrast in the field. At 2.8 the Summicron is ahead of
the Elmarit at 2.8, again in the field and in the rendition of very fine
details. This advantage is not lost at smaller apertures. So we may say that
the Summicron at 2 is already ahead of the Elmarit at 2.8 and never loses
this advantage. Given the very high performance of the Elmarit, these
differences at the smaller apertures are not very great, but they are there
for the discerning user to exploit.
Compared to the Summicron 2/35 ASPH, the new Summicron 2/28 wins in the
department of definition of very fine detail, where the 35mm  is of slightly
lower contrast. The Summicron 35 howver wins in the area of distortion.
Stopped down the 35mm lens is a bit softer overall, but we are here
discussing differences on a very high level of performance.
If we take a helicopter view of the Summicron line for the M, we can note
that the Apo-Summicron-M 2/90 ASPH. is the best overall and at full
aperture, closely followed by the new Summicron 2/28 ASPH. The Summicron
2/35 ASPH is third with a somewhat lower overall contrast and a softer
rendition of very fine detail at all apertures. The Summicron 2/50 upholds
its reputation at smaller apertures, but begins to show its age at full
aperture performance.
Well even Pete Sampras can be beaten by a younger player.

Erwin