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photo:lensmirror

super telephoto mirror lenses

introduction

  • mirror lenses are difficult to use and for most people are probably not the best option
  • they were popular in the 1970's and 80's as they mainly competed against manual focus big, heavy, f/5.6-6.3 telephoto lenses
  • in the 1990's, the advent of new high refractive index glass, computerised lens manufacture combined with a now mature autofocus technology and optical image stabiliser, meant that mirror lenses were generally only for those whose budget could not afford a “real” telephoto lens such as a 400mm f/4 IS
  • catadioptric mirror lenses share the following characteristics:
    • fixed aperture
    • virtual elimination of chromatic aberration and lateral color fringes as uses mirrors rather than lenses
      • also means focus position for infrared photography is the same as for light photography
    • central mirror:
      • allows much more compact lens length as the optic path is reflected internally twice
      • by necessity, blocks some of the light and thus causes:
        • decrease in image contrast
        • characteristic ugly “donut” shaped bokeh imagery in out of focus areas
    • front filter thread if present, rotates with focus
    • significant vignetting
    • difficult to suppress stray light, ghost and flare
    • shallow depth of field (DOF) with low contrast makes accurate manual focus difficult, further compounded on most lenses by the lack of micro-focus gearing so that only small incremental changes to focus can be made
  • apart from their telephoto reach for such a small size, these lenses were difficult to use for film photographers using SLR cameras as:
    • they usually had slow apertures around f/8 and were thus dim in optical viewfinders making manual focus difficult and requiring bright sunny conditions for any action shots
    • they were not image stabilised, and the light weight actually worked against getting sharp images without camera shake - even the camera's mirror was sufficient to cause camera shake

mirror lenses on mirrorless cameras

  • mirrorless camera systems cameras address many of the issues of mirror lenses by:
    • using an electronic view finder with magnified, image stabilised manual focus +/- manual focus peaking
    • no mirror to cause mirror-induced camera shake which is a big problem in SLRs and dSLRs at high magnification work such as when using these lenses
    • image stabiliser built-in such as the Olympus Micro Four Thirds system
    • Micro Four Thirds system have cropped sensors which give twice the telephoto effect as they are 2x crop sensors
    • allow better image quality at high ISO levels to ISO 1600 which partly addresses the f/8 aperture issue
    • post-processing of digital images can improve the lower contrast levels these lenses give
  • the Carl Zeiss Contax 500mm f/8 is said to be the sharpest with best contrast but these are also the most expensive and are quite rare
  • if small size, light weight and high image quality are your main requirements, then the Olympus OM 500mm f/8.0 mirror lens and the Minolta Rokkor RF 250mm f/5.6 mirror lens are the clear winners
  • However, on a Micro Four Thirds system camera, a 500mm f/8 mirror lens will be 1000mm f/8 and you should weigh this up against use of refractor style lenses such as:

mirror lenses

2000mm

1000mm or more

600-800mm

500mm

<500mm

cheaper designs

comparison of 500mm mirror lenses

model aperture diam length length incl. MFT adapter weight optics close focus front filter Infinity on Canon EOS
Olympus OM f/8 81mm 97mm 123mm 590g v. good 4m 72mm YES
Canon FD f/8 90mm 148mm 170mm 705g v.good 4m none NO
Nikkor N f/8 89mm 116mm 143mm 823g v. good 1.5m 82mm YES
Nikkor C f/8 93mm 142mm 169mm 1000g good 4m 88mm YES
Sony/Minolta f/8 89mm 118mm 142mm 665g v. good 4m 82mm NO
Tamron SP f/8 f/8 84mm 92mm mm 595g good? 1.7m 82mm YES
Samyang f/8 f/8 77mm 88mm 123mm 320g avg? 1.7m 72mm YES
Samyang f/6.3 f/6.3 119mm 98mm 133mm 705g avg? 2m 95mm YES
ProOptic Maksutov f/5.6 105mm 220mm 255mm 1220g good 1.5m slow but microtune none YES
photo/lensmirror.txt · Last modified: 2014/05/18 10:03 by gary1