Archived posting to the Leica Users Group, 2013/02/03
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks for the lesson..... Now maybe a 35 f0.47 sounds good, but only if you own a Nocti to begin with..... More practical for a greater segment of the market is......a 50 Summilux with this gizmo... Imagine $600 + 50 Summilux = 35mm Noctilux... now there is something I can sink my teeth into.... If only they made one for the M Mount.... Frank Filippone Red735i at verizon.net -----Original Message----- From: lug-bounces+red735i=verizon.net at leica-users.org [mailto:lug-bounces+red735i=verizon.net at leica-users.org] On Behalf Of Howard Ritter Sent: Sunday, February 03, 2013 11:44 AM To: Leica Users Group Subject: Re: [Leica] speed booster Well, no. But a 35mm f/0.47, yes. The Metabones is a focal reducer, the opposite of a tele-extender. Such are well known to astroimagers for increasing the field of view of a telescope and the brightness of the image it produces. If you use a positive lens to reduce the effective focal length of an objective without restricting the aperture, you have lowered the f-ratio. And that's what the Metabones does: reduce the focal length by a factor of 0.71, which is approximately = v2/2. Since the brightness of an image at a given f.l. varies with the square of the aperture (therefore inversely with the square of the f-ratio), reducing the f.l. by a factor of v2/2 thus brightens the image by a factor of 2, or a full f-stop. Question is, does the Metabones have the throat (entrance pupil I believe) that would be required to accommodate the huge light cone from the full-open Nocti? It's related to the annoying fact that no passive optical assistance will make an object appear brighter than it would be to the naked eye at a distance where the object would appear the same size as the optic makes it appear. No free lunches in optics. Gaining any reduction in f-stop without decreasing the f.l., now that would be magic! howard On Feb 3, 2013, at 1:40 PM, Frank Filippone <red735i at verizon.net> wrote: > Can you imagine a 50mm F0.47 lens? > > Oh please, an M mount on both sides? > Pretty please? > > On a similar note.... I just found my Komura Telemore II 2x Extender > for M cameras..... need to take it out for a test with the M9.... if > it focuses well, WOW! > I can stand some image degradation.. but out of focus drives me nuts.... > It came with a Komura LTM-M adapter... to which I have several genuine > and non genuine adapters... must try a few to see if one works better > than the others.... > > Frank Filippone > Red735i at verizon.net > > any thoughts on this :" > > http://www.metabones.com/info/105-info/154-speed-booster > > brgds > Simon > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information