photo:lensmirror
Table of Contents
super telephoto mirror lenses
see also:
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:
- manual focus (apart from the Sony / Minolta AF Reflex 500mm f/8.0 mirror lens)
- 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:
- Olympus ZD 50-200mm f/2.8-3.5 lens with EC-20 2x teleconverter which gives 200-800mm f/5.6-7, is weathersealed and will autofocus when used with a Olympus Four Thirds dSLR system or a Micro Four Thirds system with phase detect AF such as the Olympus OM-D E-M1
- this will give much more versatility and far better bokeh but will weigh much more, look much longer when at full telephoto, and cost much more
- total length of this combo on Micro Four Thirds is 217mm but lens extends to almost double at maximum zoom
- total weight ~1.1kg
- filter thread 67mm
mirror lenses
2000mm
- see also Schmidt-Cassegrain telescopes eg. 8“ f/10 Meade or Celestron SCT telescopes
1000mm or more
- MTO-11CA 1000mm f/10 - Russian
600-800mm
500mm
- Carl Zeiss Contax 500mm f/4.5 Mirotar T* mirror lens - rare, expensive
- Rubinar 500mm f/5.6 mirror lens - Russian
- Carl Zeiss Contax 500mm f/8.0 Mirotar T* mirror lens - rare, expensive
<500mm
-
- not very sharp
- Rubinar 300mm f/4.5 mirror lens - Russian
-
- one of the few mirror lenses with focal length < 500mm that is worth buying, but they sell now for very high prices 2nd hand - eg. $1400!!
cheaper designs
- older cheap brands include Hanimex, Makinon, Soligor
- contemporary cheap models with generally lesser image quality and build quality, and often marketed as Albinar, Vivitar, Rokinon, Bower, Walimex, etc, include:
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 20:03 by gary1