Help with Birns & Sawyer Range Finder IIIB

[Vadim Joy]

Hello, I purchased an old Birns & Sawyer Range Finder (Model IIIB) on my last trip to Los Angeles. I still can't properly figure out how to use it. It has a table on the side, any help on how to read it?

 

[Vadim Joy]

And what does f= stands for? (18.5,25,35,40,50,75,85,100,125,135,150,200)

 

It goes like this:

f=

Normalfilmu. Breitwand

Cinema-scope 2.55 and 2.33

Vista Vision

T.V. Riesel -Jkon and Jmaqe-Orth

[Mark Dunn]

Despite the name it's not a rengefinder, it's a director's viewfinder.

f denotes the lens focal length and the figures are aspect ratios- presumably you know what 'scope is. Breitwand is German for widescreen.

The front ring alters the masking for non-anamorphic widescreen- 1.85, 1.75 and 1.66:1 as it says.

'TV' refers to obsolete tube types- I recognise image orthicon and the table is a conversion table for the various aspect ratios and focal lengths.

[Vadim Joy]

Despite the name it's not a rengefinder, it's a director's viewfinder.

f denotes the lens focal length and the figures are aspect ratios- presumably you know what 'scope is. Breitwand is German for widescreen.

The front ring alters the masking for non-anamorphic widescreen- 1.85, 1.75 and 1.66:1 as it says.

'TV' refers to obsolete tube types- I recognise image orthicon and the table is a conversion table for the various aspect ratios and focal lengths.

Thanks Mark. I still don't get it. Say I set it to 2.33:1, how do i read table? Does it mean that at 2 I'm having 40mm and at 80 I'm having 200mm? Because I seems wrong to me. See pic.

 

[Mark Dunn]

Maybe you set the numbered scale to 2 and that gives you the FoV for a 40mm? The scale is evidently non-linear.

Perhaps you can compare it with the FoV on a dslr.