wat are mirror lens use for ?


Status
Not open for further replies.

zac08

Senior Member
Feb 21, 2005
11,755
0
0
East
#2
hi guys as i nv get to use those lens b4 , so would like to ask wat are those mirror lens for ? thx :)
A mirror lens is used for situations when you can't use such a long lens and yet, you still want a long focal length... By using a mirror system, you effectively cut the lens length in half or so...
 

oTaRu

New Member
Dec 25, 2004
1,272
0
0
#3
meaning a 400mm lens with the mirror system can go to 800mm focus length?
 

dscans

New Member
Sep 10, 2007
34
0
0
#4
A miror lens used to be called a "poor man's telephoto", in that you can get quite impressive focal lengths without breaking out a 2nd mortgage for an equivalent "normal" telephoto lens. Mirror lenses typically start from 500mm and up. I have a 600mm Sigma mirror lens.

A mirror lens is also more compact than a normal telephoto lens because it uses mirrors to "fold" or reflect light internally. Although it may be shorter, the use of internal mirrors make such lenses a "fatty". The circumference of a mirror lenses is typically pretty big. Since the internal light path is reflected off mirrors, there are no complicated optical hurdles to overcome. A normal telephoto lens can have 8-10 optical elements, and it involves a lot of precision engineering in the manufacture. The simpler construction in a mirror lens thus makes it cheaper.

It's not all great news though. Other than the relatively low cost, there are some significant disadvantages. Mirror lenses typically have fixed apertures, typically between F8 to F11, although there are some faster F5.6 lenses. So it's not a fast lens by any means, and you really need good light to get decent results. Contrast is also not that great, as image quality is affected each time the light gets reflected.

You also lose the auto-focus of your camera, as most AF modules to not work properly beyond F5.6. Lastly, mirror lens do not have good bokeh. Instead of a nice, smooth blurred background, you get strange, circular donut shaped highlights. This comes about from the internal mirrors used in the lens body.

Mirror lenses are nice lens to play with though :)
 

BigRooster

New Member
May 13, 2007
206
0
0
Singapore
#8
may i noe where to get those lens ?
You may wish to consider the pros and cons of mirror lens before getting it. Getting reasonably sharp pic (subject to good lighting and steady hand/support) is attainable, but it would definitely not be comparable to the telephoto prime lens.

Many shops here do not sell them, but you may be able to get the Kenko 500mm f/6.3 DX mirror lens from Orient Photo, at slightly below $500.
 

dscans

New Member
Sep 10, 2007
34
0
0
#9


This is the 600mm Sigma I own. It's for the Canon mount. I think it has been discontinued....at least, I don't find it anywhere in the Sigma website.

Pretty compact length wise for a 600mm, but a real fatty in bulk :)
 

HydroPoP

New Member
Jun 18, 2002
956
0
0
hydrop.multiply.com
#10
I guess the only mirror lens that is sold new by a major brand is the Sony (Minolta) 500mm F8 mirror lens. Available at most sony outlets. ;p
 

cjtune

New Member
Mar 20, 2006
1,519
0
0
#11
I think you can get many generic brand-name 500mm mirror lenses off Ebay for under S$100 or a bit more. Most are fully-manual-focus, and note also that you can't use your normal lens filters for mirror lenses. You need special ones that fit to its mount-side.
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#12
You also lose the auto-focus of your camera, as most AF modules to not work properly beyond F5.6. Lastly, mirror lens do not have good bokeh. Instead of a nice, smooth blurred background, you get strange, circular donut shaped highlights. This comes about from the internal mirrors used in the lens body.
The donut shaped bokeh comes about from the light obstruction by the central secondary mirror in the corrector plate in front.
 

LittleWolf

New Member
Jan 23, 2005
1,095
0
0
Singapore
#14
Mirror lenses typically have fixed apertures, typically between F8 to F11
Note the word "typically" - there are full-mirror tele lenses with variable aperture ...

Instead of a nice, smooth blurred background, you get strange, circular donut shaped highlights.
... and with "normal", disc-like circles of confusion. They may be quite rare, though. I'm aware of a German company marketing such a 500 mm lens in the 1970s.

You may wish to consider the pros and cons of mirror lens before getting it. Getting reasonably sharp pic (subject to good lighting and steady hand/support) is attainable, but it would definitely not be comparable to the telephoto prime lens.
Most mirror lenses ARE telephoto prime lenses, and they can be very sharp (there's quite a bit of overlap between photographic mirror lenses and astronomical mirror telescopes, where sharpness is the main requirement). What limits sharpness is frequently not the lens, but the vibrating support and/or atmospheric turbulence (the latter in particular if you shoot in a horizontal direction in warm climates).

Also note that (pure) mirror lenses are completely free from chromatic abberration (colour fringing).

Most are fully-manual-focus, and note also that you can't use your normal lens filters for mirror lenses. You need special ones that fit to its mount-side.
Some mirror lenses do have standard filter threads. I have a 1000mm f/10 that even came with a set of filters.

What can be a problem with modern cameras is the trend to have bulky grips. These might mechanically interfere with large-diameter mirror lens barrels.
 

ctloh

New Member
Oct 11, 2007
2
0
0
#15


This is the 600mm Sigma I own. It's for the Canon mount. I think it has been discontinued....at least, I don't find it anywhere in the Sigma website.

Pretty compact length wise for a 600mm, but a real fatty in bulk :)
Hi dscans,

I saw your Sigma 600mm reflex lens post. Not sure where do you get it ? do you think it is still available now ?

Are you willing to sell of your unit ? :p.... just asking... no offense.

ctloh
 

Status
Not open for further replies.
Top Bottom