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Author Topic: The anti-extension tube: EF-S adapter for EF lenses  (Read 1418 times)

bchernicoff

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The anti-extension tube: EF-S adapter for EF lenses
« on: March 20, 2012, 02:44:50 PM »
I have a theoretical question for any of you with a working knowledge of lenses/optics.

If an extender works by taking the central part of a lens's image circle and enlarges it to cover the whole sensor(thus magnifying and reducing brightness), shouldn't it be possible to create an adapter for crop sensor cameras that uses the entire image circle of a full-frame lens and reduces it to the size of the cropped sensor to gain the full angle of view? Would the resulting smaller light circle also be brighter since it's focused onto a smaller area?
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The anti-extension tube: EF-S adapter for EF lenses
« on: March 20, 2012, 02:44:50 PM »

Mt Spokane Photography

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Re: The anti-extension tube: EF-S adapter for EF lenses
« Reply #1 on: March 20, 2012, 08:19:53 PM »
It sounds like you want a wider view from your lens.  You can get screw on wide angle adapters to give you a wider view.
 
Its probably possible to design a extender to do something like that, but it would be better to just get a wider lens.  I doubt if we would ever see something like that. but who knows?

Stephen Melvin

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Re: The anti-extension tube: EF-S adapter for EF lenses
« Reply #2 on: March 20, 2012, 08:35:38 PM »
I have a theoretical question for any of you with a working knowledge of lenses/optics.

If an extender works by taking the central part of a lens's image circle and enlarges it to cover the whole sensor(thus magnifying and reducing brightness), shouldn't it be possible to create an adapter for crop sensor cameras that uses the entire image circle of a full-frame lens and reduces it to the size of the cropped sensor to gain the full angle of view? Would the resulting smaller light circle also be brighter since it's focused onto a smaller area?


Yes, it's technically possible. But Kodak owns all of the patents, so nobody's going to make one. As well, there's no "universal" adapter possible; they'd need to make different versions for different exit pupil locations.

And one last thing: because of physical limitations, f/2.8 is probably the brightest one of these adapters can do. Possibly f/2.0.

As an aside; that's exactly how Olympus makes their 35-100 f/2.0 lens. It's optically a 70-200 f/2.8 with a .5x converter built-in. In theory, it should be a 35-100 f/1.4 -- it's certainly as big, heavy and as expensive as one.

bchernicoff

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Re: The anti-extension tube: EF-S adapter for EF lenses
« Reply #3 on: March 20, 2012, 09:24:31 PM »
It sounds like you want a wider view from your lens.  You can get screw on wide angle adapters to give you a wider view.
 
Its probably possible to design a extender to do something like that, but it would be better to just get a wider lens.  I doubt if we would ever see something like that. but who knows?

I do not own a crop sensor camera. This was an idea I had and just wondered if it were possible.
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bchernicoff

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Re: The anti-extension tube: EF-S adapter for EF lenses
« Reply #4 on: March 20, 2012, 09:26:44 PM »
As an aside; that's exactly how Olympus makes their 35-100 f/2.0 lens. It's optically a 70-200 f/2.8 with a .5x converter built-in. In theory, it should be a 35-100 f/1.4 -- it's certainly as big, heavy and as expensive as one.

Thanks. This is exactly what I was looking for. It is possible and some is doing it, though not in a universal sense.
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Tamron 24-70 2.8 VC, Canon 50mm f/1.2L, 70-200 f/2.8L IS II, 400mm f/2.8L II, 100mm L IS Macro, Sigma 85mm, & 35mm f/1.4's, Rokinon 14mm f/2.8, Canon 2x Extender II, Kenko 1.4x, 430 EX II, Elinchroms

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Re: The anti-extension tube: EF-S adapter for EF lenses
« Reply #4 on: March 20, 2012, 09:26:44 PM »