Archived posting to the Leica Users Group, 2000/08/04
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 length. 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. Miro > 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 >