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Leica R-Lenses
by Erwin Puts
January 2004
Chapter 7: 28-90 mm lens
__ LEICA VARIO-ELMARIT-R 28-90 MM F/2.8-4.5 ASPH
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Chapter 7 Leica R-Lenses 1 __Introduction The zoomlens as a species of lens design has had a strange movements of the lens mount. evolution. The first design seems to be the Vario-Glaukar This new Leica zoomlens has a number of innovative featu- 1:2.8/25-80 mm for 16 mm cine cameras, created by res that elevates zoomlens design to a new level. Siemens around 1936. Especially in movies, the idea of a smoothly changing rate of magnification is very valuable as It is the first Leica zoomlens that
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Chapter 7 Leica R-Lenses 2 __ LEICA VARIO-ELMARIT-R 28-90 MM F/2.8-4.5 ASPH __Zoomrange The choice of focal lengths is very practical. Many years wish would have clashed with the desire for a compact lens. ago Canon has analysed thousands of photographs and Remember that the famous Vario-Elmarit-R 35-70 mm f/2.8 concluded that the most often used apertures and speeds had a front diameter of 88 mm and extrapolating this to the are 1:8 and 1/125 and that the most used focal lengths 90 mm position,
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Chapter 7 Leica R-Lenses 3 __Optical demands and mechanical con- struction The design has 11 elements in 8 groups and employs two the accuracy of assembly is a jump from nanometer scale aspherical surfaces, one at the first surface of the front ele- to micrometer scale (0.001 mm), but this micrometer scale ment and one at the second surface of the last element, is still incredibly small. And the designer must be aware of incidentally the same as in the original Noctilux 50 mm this jump to assur
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Chapter 7 Leica R-Lenses 4 allow the people at the assembly line to hand adjust the selected because the surface reacts quite well to the black compensator mechanism in such a way that the lens is anodizing process (see image 1). always at optimum performance. Every single lens is being checked to perform as designed and especially the aspheri- cal elements are very carefully adjusted. The result is a much lower tolerance band than would normally be possi- ble. The care that is being lavished o
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Chapter 7 Leica R-Lenses 5 of fine detail. Stopping down to 5.6 the performance of the Aperture Stop 2.8 [%] centre now extends over an image circle of 12 mm diameter 100 (see image 3). There is no trace of astigmatism and a slight field curvature. Some colour fringing is visible at very 80 high magnifications. Distortion is visible with -3% (barrel distortion) and so is vignetting at 2.5 stops (see image 4). 60 At 35 mm and full aperture (2.8) there is a small improve- 40 ment in the outer zo
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Chapter 7 Leica R-Lenses 7 Aperture Stop 3.4 Aperture Stop 2.8 [%] [%] 100 100 80 80 60 60 40 40 20 20 0 0 0 5 10 15 20 0 5 10 15 20 Y'[mm] image 5 image 8 Y'[mm] Aperture Stop 5.6 Aperture Stop 5.6 [%] [%] 100 100 80 80 60 60 40 40 20 20 0 0 0 5 10 15 20 0 5 10 15 20 Y'[mm] image 6 Y'[mm] image 9 Relative Distortion Relative Distortion [%] [%] 5 5 4 4 3 3 2 2 1 1 0 0 -1 -1 -2 -2 -3 -3 -4 -4 -5 -5 0 5 10 15 20 0 5 10 15 20 Y'[mm] Y'[mm] image 7 image 10
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Chapter 7 Leica R-Lenses 8 Aperture Stop 4.0 Aperture Stop 4.5 [%] [%] 100 100 80 80 60 60 40 40 20 20 0 0 0 5 10 15 20 0 5 10 15 20 Y'[mm] image 11 Y'[mm] image 14 Aperture Stop 5.6 Aperture Stop 5.6 [%] [%] 100 100 80 80 60 60 40 40 20 20 0 0 0 5 10 15 20 0 5 10 15 20 Y'[mm] image 12 Y'[mm] image 15 Relative Distortion Relative Distortion [%] [%] 5 5 4 4 3 3 2 2 1 1 0 0 -1 -1 -2 -2 -3 -3 -4 -4 -5 -5 0 5 10 15 20 0 5 10 15 20 Y'[mm] image 13 image 16 Y'[mm]
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Chapter 7 Leica R-Lenses 9 This is a lens with amazing characteristics. It offers outstan- and if you have not yet tried slide film, the acquisition of ding quality and can be compared very favourably to the this lens might be a good incentive to try these films. fixed focal lengths. A detailed comparison with the equiva- lent fixed focal lengths is possible based on the published The wide zoomrange from 28 to 90 mm highlights another graphs in earlier chapters and in the lens data sheets, avai
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Chapter 7 Leica R-Lenses 10 __Flare properties I made a special study of the flare properties of the lens, as The image quality of the LEICA VARIO-ELMARIT-R 28-90 this is the one area where lenses have to go 'a bout de MM F/2.8-4.5 ASPH is generally above what one expects souffle'. Veiling glare is hardly visible at all focal lengths, from high grade fixed focal lengths and the focal length implying there is no loss of contrast when the background range secures it a premium role in the Leica R l
