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Author Topic: A "fast" lens  (Read 1479 times)

Edalongthepacific

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A "fast" lens
« on: July 15, 2012, 10:05:40 pm »

What is a fast lens? I would say any lens between f/1.2 and f/2.8. Agree?
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scooby70

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Re: A "fast" lens
« Reply #1 on: July 15, 2012, 10:23:31 pm »

But why rule out anything "faster" than f1.2?

How about... faster = faster than f2.8?

:D
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Edalongthepacific

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Re: A "fast" lens
« Reply #2 on: July 15, 2012, 10:40:35 pm »

Well, I guess I was thinking that for all practical purposes an f/1 lens was unavailable. Can an f/1 lens be made and priced within reasonable limits? I have heard that there are lenses faster than f/1 but how can that be?
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Sareesh Sudhakaran

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Re: A "fast" lens
« Reply #3 on: July 15, 2012, 11:33:36 pm »

I think the fastest lens ever is the Zeiss 50mm f/0.70, used for Barry Lyndon by Stanley Kubrick.
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Jim Pascoe

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Re: A "fast" lens
« Reply #4 on: July 16, 2012, 06:14:30 am »

Well, I guess I was thinking that for all practical purposes an f/1 lens was unavailable. Can an f/1 lens be made and priced within reasonable limits? I have heard that there are lenses faster than f/1 but how can that be?

Well I have a Voightlander 25mm f0.95 and it is currently available in Micro 43 mount.  Great lens - you will find a review of it somewhere on LL.  They have also just released a 17mm lens also f0.95.  (these are equivalent to 50mm and 35mm in full frame).

Jim
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mediumcool

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Re: A "fast" lens
« Reply #5 on: July 16, 2012, 12:35:27 pm »

I think the fastest lens ever is the Zeiss 50mm f/0.70, used for Barry Lyndon by Stanley Kubrick.

… and for shots of the dark side of the moon. Cue Pink Floyd.  ;D
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ErikKaffehr

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Re: A "fast" lens
« Reply #6 on: July 17, 2012, 09:25:32 am »

Hi,

F-stop is aperture divided by focal length. Increasing the opening of the lens so it is larger than the focal length will make for F-stop < 1.

I'm not sure there is a theoretical limit, although it may do with total reflection at certain angles, but that would only occour on glass air surfaces, I think.

Best regards
Erik

Well, I guess I was thinking that for all practical purposes an f/1 lens was unavailable. Can an f/1 lens be made and priced within reasonable limits? I have heard that there are lenses faster than f/1 but how can that be?
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Erik Kaffehr
 
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