Re: [Leica] The 0.85: strange new need

[Dennis Painter <dwp@deltanet.com>]

Erwin Puts wrote:
> 
> THis is my message from some time ago:
> 
> There is a mechanical/optical relationship between the accuracy of the
> rangefinder and the baselength in relation to the maximum aperture/.
> The equation will be published elsewhere, but here is the result:
> 
> Focal length    Max aperture    Max aperture
>                 M3              M2, M4, M5, M6
> 21 mm           0.12            0.15
> 28 mm           0.21            0.26
> 35 mm           0.33            0.41
> 50 mm           0.67            0.84
> 75 mm           1.5             1.88
> 90 mm           2.17            2.71
> 135 mm          4.88            6.1
> 
> This equation then tells you that the 21 mm can be reliably focused when the
> maximum aperture is f/0.12 (incredible!).
> At 50mm the Noctilux approximates the theoretical maximum values when
> attached to the M6.
> The 135mm seems to be overstretched when used at its maximun aperture of 2,8.
> Hope this info has some value
> 
> As you can infer frm these figures, fully reliable measurements are nor a
> problem with the 2,8/90 on any M, but using the Summilux  75 is a bit
> demanding on the rangefinder.
> Erwin

Erwin,

This has to be at a specific distance right?  I would assume at 1 metre.

Dennis


- -- 
Experience is a tough teacher. It gives the test before the lesson.
- -unknown