Luminous Landscape Forum

Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: Edalongthepacific on July 15, 2012, 10:05:40 pm

Title: A "fast" lens
Post by: Edalongthepacific 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?
Title: Re: A "fast" lens
Post by: scooby70 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
Title: Re: A "fast" lens
Post by: Edalongthepacific 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?
Title: Re: A "fast" lens
Post by: Sareesh Sudhakaran 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.
Title: Re: A "fast" lens
Post by: Jim Pascoe 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
Title: Re: A "fast" lens
Post by: mediumcool 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
Title: Re: A "fast" lens
Post by: ErikKaffehr 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?