I'm positive that they had an old 300/2.8.Originally Posted by Daniel Browning
A used Sigma 300mm f/2.8+2X would do better than the zooms. Sometimes a used Sigma 500mm f/4.5 will come around for $2,900, but that's over budget. I thought Tamron had some nice old prime teles, but I don't see them.
How do they work? I've never heard of such a thing. []
It's the same thing as a focal reducer (or field flattener), which are used all the time in astrophotography, except with a few extra elements to preserve the backfocus distance.
They're like the inverse of a teleconverter. They mount between the lens and camera, but instead of making the focal length longer and f-number slower, they make the focal length shorter and f-number faster. They need about 7 elements, same as a good TC, but thicker, and it needs to be matched specifically for a single lens.
It would be ideal for wildlife because most of the time we'll want super long focal lengths (e.g. 1100mm) with the highest quality possible. An 1100mm f/11 L IS with no TC would provide that quality (and even allow another 1.4X TC), and for those rare times when it's too long or you need autofocus, you pop on the wide converter to get 550mm f/5.6, though the quality is lower.
One example is the Oly 35-100 f/2.0, which is actually just a typical 70-200 f/2.8 lens with a wide converter permanently attached: that's why it's over two times heavier than a 35-100 f/2 should be. It should have turned out as a 35-100 f/1.4, but they left it at f/2 for some reason (I heard that if you press the lens release, it opens to f/1.6 but vignettes terribly -- perhaps that's why).
Unfortunately, I don't think we'll see any until the Kodak patent expires.
Interesting. Thanks, Daniel.
100-400 f4.5L IS (new $1600)
100 2.8L IS (new $1050)
Posting Permissions
Reply With Quote