Archived posting to the Leica Users Group, 2000/08/04

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Subject: [Leica] Re: 50/1.2 or 50/1.5 or 50/2?!
From: "Miro Jurcevic" <>
Date: Sat, 5 Aug 2000 09:54:29 +1000
References: <>

My understanding from what I have been told about lenses, is that the light
geometry of different focal lengths determines the F-stop for that focal

Essentially, it is possible to have a different exposure for 50mm f2 and
85mm f2, since the f-stop is a ratio of focal length to lense diameter. The
longer focal length is metering a smaller area of the same space and would
in effect be metering less light per given area.

Secondly, there is no similarity between the three metering systems and the
bias toward factory settings. Unless we are using a single scientific meter
will all four objectives.

Thirdly, variations in angle of observation, even angles less than 10
degrees, can alter the reflected angle entering the metering system.

These comments are based on the physics of the scene that you have
described. There is simply more than one variable being tested.


> Canon 50/1.5 @f/2 = Between 1/250 and 1/500 sec
> Nikkor 85/2 @ f/2  = 1/250 sec
> M-Hexanon 50/2 @f/2 = 1/250 sec
> M-Hexanon 90/2.8@ f/2.8 = 1/125 sec

Replies: Reply from Dante A Stella <> (Re: [Leica] Re: 50/1.2 or 50/1.5 or 50/2?!)
In reply to: Message from Dante A Stella <> ([Leica] 50/1.2 or 50/1.5 or 50/2?!)