Old Lens Question- Old F/Stop Markings?

[Roger Hicks]

Actually there were at one time 3 different f-stop scales: American, British, & French. But they were all f-stops the starting point was different.

Before that there were several different aperture systems, none of which were base on f-stops. You really have to do your research to figure those out. However, most of those date from before the 1920's.

Any meter that reads in 1/3 stops can be easily used with any of the f-stop systems. Except the early Westons, which used a different index than ASA/ISO. However they worked OK for B&W. For slides you had to convert your ASA rating to Weston ratings.

There was a time when you really had to be knowledgable to be a photographer. Now you don't even need a camera just a smart phone.

Ah... One of them Uniform System, inexplicably abbreviated to US.

But the stops remain constant (with varying rounding corrections) regardless of what film speed you're using: Kodak/ASA, DIN, Weston, GOST, Schneider, BS...

I'm not familiar with a specifically American stop system: just one based on f/1 (UK and US), and the so-called "Continental" system, 1/3 stop different. What had you in mind as a specifically American sequence?

Cheers,

R.

 

[JPD]

When you use a camera with the older set of speeds (1-2-5-10-25-50-100-250) it's even more simple to use the old aperture scale. If your lightmeter reads 1/125 sec and f:8, use 1/100 and f:9.

Shutter speeds are almost always a little slower than the marked ones anyway.

What do you mean by "equivalent F/stops"? It's a linear, continuous scale. So f/8 is right in the middle between your 6.8 and 9 marks.

Some shutters have the mark for f:7,7 there.