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of fine detail. Stopping down to 5.6 the performance of the
centre now extends over an image circle of 12 mm diameter
(see image 3)
. There is no trace of astigmatism and a
slight field curvature. Some colour fringing is visible at very
high magnifications. Distortion is visible with -3% (barrel
distortion) and so is vignetting at 2.5 stops
(see image 4)
.
At 35 mm and full aperture (2.8) there is a small improve-
ment in the outer zones where the lens now records 100
lp/mm with good micro-contrast
(see image 5)
. Distortion
now is about -1%. At 5.6 we have optimum performance
with a crisp rendition of very fine detail over most of the
image area
(see image 6)
. Vignetting is practically gone
(see image 7)
.
At 50 mm and full aperture (3.4) we see a very high con-
trast and an exceptionally high resolving power of more
than 150 lp/mm over a large section of the negative. There
is still some faint colour fringing, but in practice one would
be very hard pressed to note it
(see image 8 and 10)
. At
5.6 we have impeccable performance that easily surpasses
the quality of the Summicron 50 mm lens, especially in the
outer zones of the field
(see image 9)
.
At 70 mm and full aperture (4) the image quality becomes
superb and we have an extremely high contrast and a very
crisp definition of the finest details
(see image 11)
.
Stopping down to 5.6 does improve edge contrast and now
the corners are quite good too
(see image 12)
. Distortion
is 1% (pincushion) and vignetting negligible
(see image 13)
.
At 90 mm and full aperture (4.5) the best performance is
reached and compared to the 70 mm position the outer
zones and corners are now as good as the centre of the
image
(see image 14)
. Vignetting is gone and distortion is
very low with 1%. The low distortion at the tele side of the
zoomrange is quite remarkable. Often the behaviour of
zoomlenses can be characterized as good in the middle
range and weaker at both extremes
(see image 15 and
16)
.
Chapter 7 Leica R-Lenses 5
0 5 10 15 20
Y'[mm]
0
20
40
60
80
100
[%]
Aperture Stop 2.8
0 5 10 15 20
Y'[mm]
0
20
40
60
80
100
[%]
Aperture Stop 5.6
image 2
image 3
0 5 10 15 20
Y'[mm]
-5
-4
-3
-2
-1
0
1
2
3
4
5
[%]
Relative Distortion
image 4