Rapid Angulaire Lens

[Ole Tjugen]

If the holes are 10, 8, 4 and 2mm and the focal length is 100mm, then the apertures are as follows:

100/10 = 10
100/8 = 12.5
100/4 = 25
100/2 = 50

So f:10, f:12.5, f:25, and f:50.

Do not assume that old lenses will have apertures in the "standard modern series" - f:8, f:11, f:16, f:22 and so on. There were many different "series" in se, and many do not even follow THOSE!

French lens makers seem to have had a preference for this series, ending at a nice even f:100. The 12.5, 25, 50 is rather common.

[seawolf66]

thank you very much Ole. well that should be fun with a Light meter, the funny part is this lens could almost fit in a watch pocket
thanks again Ole :

If the holes are 10, 8, 4 and 2mm and the focal length is 100mm, then the apertures are as follows:

100/10 = 10
100/8 = 12.5
100/4 = 25
100/2 = 50

So f:10, f:12.5, f:25, and f:50.

Do not assume that old lenses will have apertures in the "standard modern series" - f:8, f:11, f:16, f:22 and so on. There were many different "series" in se, and many do not even follow THOSE!

French lens makers seem to have had a preference for this series, ending at a nice even f:100. The 12.5, 25, 50 is rather common.

[premortho]

If you have a Weston Master, it has a lot of the "other" f-stops on the dial. Even if it does'nt work any more, just set the Weston to agree with your working meter, than read off the exposure at-or-close to your f-stops on the rotary wheel stops.

thank you very much Ole. well that should be fun with a Light meter, the funny part is this lens could almost fit in a watch pocket
thanks again Ole :