Instruction/ maintenance manual of the product R-Lenses Leica
Go to page of 10
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.
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.
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.
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 .
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.
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.
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.
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.
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 .
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.
An important point after buying a device Leica R-Lenses (or even before the purchase) is to read its user manual. We should do this for several simple reasons:
If you have not bought Leica R-Lenses yet, this is a good time to familiarize yourself with the basic data on the product. First of all view first pages of the manual, you can find above. You should find there the most important technical data Leica R-Lenses - thus you can check whether the hardware meets your expectations. When delving into next pages of the user manual, Leica R-Lenses you will learn all the available features of the product, as well as information on its operation. The information that you get Leica R-Lenses will certainly help you make a decision on the purchase.
If you already are a holder of Leica R-Lenses, but have not read the manual yet, you should do it for the reasons described above. You will learn then if you properly used the available features, and whether you have not made any mistakes, which can shorten the lifetime Leica R-Lenses.
However, one of the most important roles played by the user manual is to help in solving problems with Leica R-Lenses. Almost always you will find there Troubleshooting, which are the most frequently occurring failures and malfunctions of the device Leica R-Lenses along with tips on how to solve them. Even if you fail to solve the problem, the manual will show you a further procedure – contact to the customer service center or the nearest service center
