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11-29-2009, 09:48 AM   #1
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Vivitar 800mm f8, 2 piece lens

Anyone ever heard of this lens? I was wondering if it was a good lens. It's a LONG lens not a mirrored one.

11-29-2009, 11:00 AM   #2
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I haven't seen that one specifically, but I've seen other such lenses. Sometimes they are called called pre-set, because they have no aperture control, although that's not a technically correct use of the term. They're basically refracting telescopes with a camera mount (often a T-mount so it can mount to any camera with the right adapter).

The one I actually tried - a Quantaray 600-1200 zoom - was sort of OK in sharpness considering the price (barely over $100) if you didn't pixel peep too hard, but had really bad CA compared to a mirror lens that was just as sharp and much smaller. Some find these presets preferable to mirrors, though - especially people really put off by the "donut" bokeh of mirrors. I suppose as with all such things, there will be better and worse ones, but the basic idea of these lenses is to optimize for low cost by going with an *extremely* simple optical design, and that seldom bodes well for IQ.
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