Can a Rokinon 800mm 'mirror' lens be zoomed from 0 to 800mm OR is it fixed at 800mm ?

-This is the 'mirror' lens im planning to buy.

http://cgi.ebay.in/Rokinon-800M-B-EOS-800mm-F8-0-Mirror-Lens-Canon-EO-/270781638333?pt=LH_DefaultDomain_203&hash=item3f0bd7e6bd



I wanted to know whether it is zoomable from 0 to 800mm or it is fixed at 800mm ?It's fixed at 800mm. All mirror lenses are. Additionally the aperture will also be a fixed one, f8 in this case. All mirror lenses, except a very few really expensive ones, deliver mediocre quality. They are also inclined to produce what's called "donut bokeh" which you can clearly see in the background of this image: http://farm3.static.flickr.com/2336/2383鈥?/a>A zoom lens will always have a zoom range - 18-55mm, 55-200mm, 100-400mm. Since this lens only has one focal length - 800mm - its not a zoom lens.



I read the blog referenced by another answerer and in my opinion if you want the lens and have the money then you should buy it. Don't set your expectations too high though. Just enjoy the lens for what it is.



The blogger is right about using it on a tripod. Before lenses with image stabilization were even a dream we used the old "Shutter speed = 1/focal length" rule when hand-holding any lens. So to hand-hold this 800mm lens you'd want your shutter speed to be 1/1000 sec.



Sony has the only auto focus 500mm mirror lens available. Its actually a hold-over from the Minolta Maxxum AF lens line re-branded as a Sony. Its one of the better mirror lenses available - if you own a Sony DSLR.
All lenses with a single figure, e.g. 800mm are fixed. Zoom lenses quote two figures, e.g. 70 to 300mm. No lens zooms from "zero" to a big number, such a lens is physically impossible - all lenses start somewhere.



Given that you know so little, may I suggest that you buy from a shop, not at long distance. A good shop will be able to advise you on compatibility with your camera. It would be a bore to have to send it back because you couldn't fit it to your canmera.
I'd not buy it.. here is a blog entry about it:

http://dubiousprospects.blogspot.com/200鈥?/a>



But yes, it's fixed at 800mm, it doesn't zoom at all. Only manual focus too, and completey fixed aperture at f/8
It's fixed but don't expect the same quality as a normal lens, mirror lenses can sometimes cause a slight double image , so try before you buy.
Prime lenses like the 800 mm mirror lens has only one focal length.. It were a zoom lens, the zoom range would be listed, like 200-400 mm