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01/20/2005 08:58:16 PM · #1 |
Does anyone have or have used these lenses.Are they any good?
SIgma Zoom Super Telephoto 300-800mm f/5.6 EX APO IF HSM
Sigma Super Telephoto 600mm f/8.0 Mirror (Reflex) Manual
Vivitar Telephoto 500mm f/8.0 Mirror (Reflex) Manual Focus Lens
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01/20/2005 09:00:36 PM · #2 |
Your last two options are both mirror lenses which are notorious for not being too sharp. The first one is like a couple thousand dollars, but supposedly very good.
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01/20/2005 09:08:49 PM · #3 |
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01/20/2005 09:13:13 PM · #4 |
Mirror lenses are not necessarily poor performers. They are based on the same optical designs as Maksutov Cassegrain telescopes. All depends on the quality of the optical components, just as with standard lenses.
Mirror lenses do have really funky bokeh. Point light sources that are OOF are rendered like donuts, because of the central obstruction (from the secondary mirror). The mirror lenses are also most commonly fixed aperture, meaning you only have shutter speed and ISO to control exposure. A final thing to be careful of is that some of the mirror lenses sold are large enough in diameter and mount close enough to the camera body to interfere with the flash housing on some of the Canon DSLRs. I know that's true for 10D, I don't know if the 20D's flash projects as far forward.
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01/20/2005 09:50:55 PM · #5 |
Originally posted by Discraft:
SIgma Zoom Super Telephoto 300-800mm f/5.6 EX APO IF HSM
Sigma Super Telephoto 600mm f/8.0 Mirror (Reflex) Manual
Vivitar Telephoto 500mm f/8.0 Mirror (Reflex) Manual Focus Lens |
More than a little bit of disparity in the lenses you are looking at
The Vivitar lens is like a couple hundred dollars, Sigma reflex is a hundred or so more and the the zoom is closer to 5K. If you do have that kind of money to spend on a lens the zoom is not the way to go.
At that focal length a zoom is not an asset. Your AF speed, which is critical for wildlife photography will slow down to nothing compared to the AF on a similar prime. Take a look at the Sigma 500mm f/4.5.
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