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Leica R-Lenses manual

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Table of contents for the manual

  • Page 1

    Leica R-Lenses Januar y 2004 Chapt er 7 : 28-90 mm lens __ LEICA V ARIO-ELMARIT-R 28-90 MM F/2.8-4.5 ASPH by Er win Puts[...]

  • Page 2

    Chapt er 7 Leica R-Lenses 1 __Introduction The zoomlens as a species of lens design has had a strange evolution. The first design seems to be the V ario-Glauk ar 1:2.8/25-80 mm for 1 6 mm cine cameras, created by Siemens around 1 936. Especially in movies, the idea of a smoothly changing rat e of magnification is ver y valuable as it can dispense o[...]

  • Page 3

    Chapt er 7 Leica R-Lenses 2 __Zoomrange The choice of focal lengths is v er y practical. Many years ago Canon has analysed thousands of phot ographs and concluded that the most often used aper tures and speeds are 1:8 and 1/1 25 and that the most used focal lengths were within the 28 mm and 90 mm rang e. If we believe these studies, the new Leica l[...]

  • Page 4

    Chapt er 7 Leica R-Lenses 3 __Optical demands and mechanical con- struction The design has 1 1 elements in 8 groups and emplo ys two aspherical sur faces, one at the first sur face of the front ele- ment and one at the second surface of the last element, incidentally the same as in the original Noctilux 50 mm f/1 .2. The lens has three moving group[...]

  • Page 5

    selected because the surface reacts quite well to the black anodizing process (see image 1) . The result of all this effor t is a lens with a very smooth movement of the f ocusing ring and focal length selection. With quite sensitive fingers one can feel some ins tances of friction when you go from 90 mm to 28 mm, so perfection is alway s relative.[...]

  • Page 6

    of fine detail. St opping down to 5.6 the performance of the centre now extends o ver an imag e circle of 1 2 mm diameter (see image 3) . There is no trace of astigmatism and a slight field cur vature. Some colour fringing is visible at ver y high magnifications. Distortion is visible with -3% (bar rel distortion) and so is vignetting at 2.5 stops [...]

  • Page 7

    Chapt er 7 Leica R-Lenses 7 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 5 image 6 0 5 10 15 20 Y'[mm] -5 -4 -3 -2 -1 0 1 2 3 4 5 [%] Relative Distortion image 7 0 5 10 15 20 Y'[mm] 0 20 40 60 80 100 [%] Aperture Stop 3.4 0 5 10 15 20 Y'[mm] 0 [...]

  • Page 8

    Chapt er 7 Leica R-Lenses 8 0 5 10 15 20 Y'[mm] 0 20 40 60 80 100 [%] Aperture Stop 4.0 0 5 10 15 20 Y'[mm] 0 20 40 60 80 100 [%] Aperture Stop 5.6 image 11 image 12 0 5 10 15 20 Y'[mm] -5 -4 -3 -2 -1 0 1 2 3 4 5 [%] Relative Distortion image 13 0 5 10 15 20 Y'[mm] 0 20 40 60 80 100 [%] Aperture Stop 4.5 0 5 10 15 20 Y'[mm][...]

  • Page 9

    Chapt er 7 Leica R-Lenses 9 This is a lens with amazing characteristics. It offers outstan- ding quality and can be compared very favourably to the fixed focal lengths. A de tailed comparison with the equiva- lent fixed focal lengths is possible based on the published graphs in earlier chapters and in the lens data shee ts, avai- lable separately .[...]

  • Page 10

    Chapt er 7 Leica R-Lenses 10 __Flare proper ties I made a special study of the flare properties of the lens, as this is the one area where lenses hav e to go 'a bout de souf fle'. V eiling glare is hardly visible at all focal lengths, implying there is no loss of contrast when the background is much brighter than the subject itself. When [...]