f stops

[luis a de santos]

I have a single cell of an old Taylor Hobson lens that I have mounted on a copal 3 shutter.It has a nice bokeh and works well.I have guestimated a focal length of about +/_ 150mm.
My question is how do I determine the f stops so I can use the shutter consistantly and be able to repeat or calculate exposures.
Thank you everyone.

Luis

[John Koehrer]

f stop is a simple ratio of focal length divided by the diameter of the lens.
IE:fl/dia.=f.
If you need to make a scale, determine the maximum f# and use a light meter behind the lens to determine additional stops.
Each adjustment that gives one stop difference(EV or needle movement) in reading = 1 stop

[luis a de santos]

Ok Cool
I will do that.

Luis