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fast telephoto lens



 
 
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  #1  
Old February 15th 05, 07:57 PM
.::SuperBLUE::.
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Default fast telephoto lens

Is it possible to make a system similar to the 400mm f/2.8 for dslr cameras
out of a telescope
and a adapter? Which telescope? 150mm/ 6inch one? Which adapter?


  #2  
Old February 16th 05, 01:32 AM
Joseph Meehan
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Sure, if you have a 400mm f2.8 telescope and expect it to work only
manually. I suspect it will be a lot more convenient, better results
(optimized for a flat plan focus) and maybe even cheaper by buying a real
lens.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math
".::SuperBLUE::." wrote in message
...
Is it possible to make a system similar to the 400mm f/2.8 for dslr
cameras
out of a telescope
and a adapter? Which telescope? 150mm/ 6inch one? Which adapter?




  #3  
Old February 17th 05, 09:58 PM
Luc
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Hi,

Telescopes as Swarovski-Habicht and Kowa do have a telescope adapter but it
is at F8 or F11 : an 800mm adapter at f8 and a 1100mm adapter at f11.

Cheers,

Luc


".::SuperBLUE::." schreef in bericht
...
Is it possible to make a system similar to the 400mm f/2.8 for dslr
cameras
out of a telescope
and a adapter? Which telescope? 150mm/ 6inch one? Which adapter?




  #4  
Old February 17th 05, 09:58 PM
Luc
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Posts: n/a
Default

Hi,

Telescopes as Swarovski-Habicht and Kowa do have a telescope adapter but it
is at F8 or F11 : an 800mm adapter at f8 and a 1100mm adapter at f11.

Cheers,

Luc


".::SuperBLUE::." schreef in bericht
...
Is it possible to make a system similar to the 400mm f/2.8 for dslr
cameras
out of a telescope
and a adapter? Which telescope? 150mm/ 6inch one? Which adapter?




  #5  
Old February 18th 05, 03:56 AM
Roger N. Clark (change username to rnclark)
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..::SuperBLUE::. wrote:
Is it possible to make a system similar to the 400mm f/2.8 for dslr cameras
out of a telescope
and a adapter? Which telescope? 150mm/ 6inch one? Which adapter?


You will have a hard time getting f/2.8 from a telescope.
Telescopes with that fast of an aperture are special designs
that often have curved film planes, like Schmidt telescopes,
or would be quite expensive.

But you could get f/4.5 to f/6 effectively. I've tested
a 6-inch aperture f/6 homemade Newtonian, and it
delivers very sharp images, in fact sharper than
top end telephotos. That equates to a 914mm f/6 telephoto,
that cost only a few hundred $ to build.
The problem is focusing. If you intend to do astrophotos,
there are focusing aids (do a google search for DSLR focus),
but if you want to do wildlife photography,
where focus is constantly changing, it would not be
a good solution. Focus is very difficult with
DSLRs unless you can change the focusing screen and
can install a better microprism.

I settled for a 500 mm f/4 L IS telephoto.

Roger
Photos at: http://www.clarkvision.com

  #6  
Old February 18th 05, 03:56 AM
Roger N. Clark (change username to rnclark)
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..::SuperBLUE::. wrote:
Is it possible to make a system similar to the 400mm f/2.8 for dslr cameras
out of a telescope
and a adapter? Which telescope? 150mm/ 6inch one? Which adapter?


You will have a hard time getting f/2.8 from a telescope.
Telescopes with that fast of an aperture are special designs
that often have curved film planes, like Schmidt telescopes,
or would be quite expensive.

But you could get f/4.5 to f/6 effectively. I've tested
a 6-inch aperture f/6 homemade Newtonian, and it
delivers very sharp images, in fact sharper than
top end telephotos. That equates to a 914mm f/6 telephoto,
that cost only a few hundred $ to build.
The problem is focusing. If you intend to do astrophotos,
there are focusing aids (do a google search for DSLR focus),
but if you want to do wildlife photography,
where focus is constantly changing, it would not be
a good solution. Focus is very difficult with
DSLRs unless you can change the focusing screen and
can install a better microprism.

I settled for a 500 mm f/4 L IS telephoto.

Roger
Photos at: http://www.clarkvision.com

 




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