Fast legacy lens eqv to 35mm to 40mm

Started Jan 31, 2013 | Discussions thread
Caris Regular Member • Posts: 318
Re: Fast legacy lens eqv to 35mm to 40mm

uhligfd wrote:

Impossible question: no lens can change its focal length from camera to camera, none will do you that favor, unless you add further lenses, diopters etc to it.

So what do you want? re-collaminate an available lens? How will you compute the element arrangement? How will you keep them inside of a lens tube? Silly concept, trying to change the focal length of a lens. And then come up with a f/2 lens to boot.

Now if you by chance just want to have the field of view of a 30 mm equivalent lens on the NEX as a 30mm lens would give you on a full frame sensor, simply divide your desired FF equivalent focal length by 1.5 since the C size sensor is smaller by that factor and do look for a 20mm f/2 full frame lens.

Divide and conquer your problems ... If you want an equivalent field of view to a 50mm lens for full frame on a Nex, do the division: 50/1.5 = ..... (Hint: 50/1.5 = 50x2/3 = 100 /3 = ...)

But that lens will keep its focal length forever, no matter which camera or sensor size; your C size sensor just crops out its center part, on the NEX.

No need to rant. everybody else understood what he meant.

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