閒采兮 天然水晶 純銀飾品

Notes:

1. The Brenner catalog does not list the
   manufacturer of their CU lens. Price shown is in German Marks.
   
   
   
2. Canon Germany's sales catalog still lists the 240 (+4.2) and 450 (+2.2)
   achromatic closeup lenses in 52mm size.
   
   
   
3. Heliopan prices are US list. Dealers may sell for less. Heliopan doesn't
   make any recommendations about what lens focal lengths work best with their CU
   lenses.
   
   
   
4. The Hoya info was provided by M. Lombardi. He also stated that he has tried
   the B+W +10 diopter CU lens and that the B+W isn't achromatic and thus shows
   colour fringing. The Hoya filter is shown as being available in 58mm size on the
   THK (Hoya distributor) web page but not on B & H's page. B+W does make +1,
   +2 and +3 diopter achromatic closeup lenses in 138mm size for film/video use.
   
   
   
5. Leica info courtesy of Dieter Lefeling and Thomas Schreyegg. The prices are
   from a large German mailorder house "Wuerzburger Fotoversand" and are in German
   Marks. (Prices from August 1999).
   
   
   
6. Minolta CU lenses are designed for 50mm lenses but will work with lens FL's
   of the range indicated.
   
   
   
7. Len FL info is according to John Shaw in his book "Closeups in Nature".
   Prices updated Nov23/99 from B & H web page.
   
   
   
8. New: The IS closeup lenses without pricing info may be discontinued.
   (Additional info appreciated).
   
   
   
9. The Pentax lens info was provided by Pentax USA and prices were taken from
   the B & H web page in July 98. The Pentax CU lenses for 35mm cameras are not
   listed because they are single element lenses. The CU lenses shown are designed
   for Pentax's 645 and 67 cameras but would likely work on 35 mm camera lenses
   with the correct filter size. Pentax CU lens names are S or T followed by the
   lens focal length in centimetres. The S means that the CU lens is designed for a
   short focal length lens, generally the normal lens for that format (50mm in 35mm
   format, 75 mm in 645 format etc). The T stands for Telephoto and thus are meant
   to be used with telephoto lenses in that format (80mm and up in 35mm format
   etc). To convert the cm focal length into diopters divide 100 by the cm (eg. the
   T33 is 100/33= 3 diopters).
   
   
   
10. Reportedly is a 2-element CU lens. B & H web page shows that it works
    with a number of lenses which have differing filter sizes. A contributor reports
    the strength as +1.6 diopters and says it is of very high optical quality.
    
    
    
11. New: The Tokina lens focuses to 2.5m (equal to +0.4 diopters from
    infinity). So the add-on lens is likely less than 1 diopter (perhaps 0.4 or 0.5)
    which would give a range of focusing from infinity down to a meter or so. Tokina
    also has a CUP353 close up lens for their 35~300 zoom, but since it sells for
    $24.95 I have to presume it's not 2-element. (Corrections always appreciated.)
    
    
    
12. Reported as a 2-element CU lens in the July '96 Pop Photo mini-review of the
    100mm f3.5 lens.
    
    
    
13. Reverse mounting a 50mm lens on the front of a telephoto lens (using a
    male-male macro coupling ring, $8-$10 from B & H ) will give you extreme
    closeups. The 50mm lens is well corrected and acts like a +20 diopter CU lens.
    Mounted on a 200mm telephoto it will give you 4 times life size. There may be
    some vignetting depending on the 50mm lens speed (use it wide open). This can be
    reduced or eliminated by focusing the telephoto lens to minimum distance or by
    using a short extension tube.
    
    
    

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Lens FL refers to the focal length of the camera lens that the close up lens is
designed for. Use with a different lens FL may cause sharpness to suffer.

Diopters are the optical strength of the CU lens. Its focal length can be
calculated by using FL = 1000/Diopters. This is also the distance that will now
be in focus when the lens is focused at infinity. (A +2 diopter will bring a
subject at 1/2 metre {500mm} away into focus.)

To estimate minimum focus distance convert the camera lens minimum distance
to diopters and add it to the CU lens strength. So a +2 CU lens used with a lens
that focuses to 1 metre will act (approximately) like a +3 CU lens and bring a
subject at 1/3 metre into focus.

Another approach is to calculate magnification. Convert the diopter strength
to millimeters focal length (CU FL = 1000/Diopters). Then divide the camera lens
FL by the CU lens FL to get the magnification when the lens is focused at
infinity. Thus a +2 CU is 500mm FL. If you use it on a 50mm lens you will get
1:10 life size. The same +2 on a 300mm lens will give you 0.6 of lifesize
(1:1.66).

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