P3D Re: Mirror Lenses

[George Gioumousis <georggms@xxxxxxxxxx>]

Lawrence A. Haines wrote
> 
> Does anyone have experience with long focal length lenses that use
> mirrors ratherthan solid glass?  I notice 500 mm mirror lenses costing
> about $100 each being sold new.  They are lighter and smaller in
> diameter and in those regards would be very good for paired lens
> stereo.  Offhand it would seem that the reflected light of the mirror
> might reduce the available light, but I really do not know. Some of  the
> store people I have talked to say they are not as sharp as regular glass
> lenses, and yet there are those who say that if the lens is used at f 8
> - 22, they are just as sharp as glass lenses used at the same openings.
> I am interested in the experience of anyone who has used them.
> 
I have a 500 mm mirror lens which is nice for birds in flight, or small 
animals at a distance, and such. As far as I know, they are all fixed
aperture. Mine is officially f/8, but actually f/11 in light gathering
power because of their folded design. However, I think it is f/8 as
far as depth of field goes.

Once, when my wife and I were trying to climb Mt. Dana in Yosemite, she
said "I think that's an eagle; try to take a picture of it." I took off
my camera from around my neck, then took off my backpack, retrieved the
500 mm lens, swapped lenses (all this smoothly and carefully, so as not
to frighten the bird), and said "Where is it?" She said "It flew off 
half an hour ago!" I think she exaggerated a bit.


                           Stereo                Stereo
George Gioumousis           /---\        |       /---\ 
                             o o         |       o o  
georggms@xxxxxxxxxx           |          |         |   
(650) 494-6276              \===/        |       \===/ 
                        Photographer          Photographer


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End of PHOTO-3D Digest 2629
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