Hello,
I will admit I have probably missed something obvious but I have noticed that the actual diameter of the aperture blade opening on many of my lenses/shutters does not match the size it theoretically should be
I am using the Equation Focal Length ÷ F-Stop = Diameter of Opening
for a 210mm f/5.6 lens the diameter of the aperture at f/5.6 should be 37.5mm (210/5.6=37.5)
but I am measuring it at 32mm, its the same for several of my other LF lenses, all coming in a few mm under the theoretical dimension.
does anyone know why this could be?
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