In article <1996Jan31.151828@omega.ntu.ac.sg>, be7170013@omega.ntu.ac.sg says...

>Many seen to confuse on the lens apperture differences, E.g. the >different between f2.0 and f2.8 is a full stop not half a stop and
>the different between f2.5 and f2.8 is half a stop not a quater. Hope >the table below will helps those with apperture doubts, especically >those using manual lens where the half stop value was not engraved.
>Full Stops
>f1.0 f1.4 f2.0 f2.8 f4.0 f5.6 f8.0 f11 f16 f22 f32
>
> f1.2 f1.8 f2.5 f3.5 f4.5 f6.7 f9.5 f13 f19 f27
>Half stops

You got the whole stop sequence right, but sorely missed on the other
sequence, alas, mixing in 1/4, and 1/3 stops....
WHOLE STOPS: 0.7, 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90,
128, 180, 256, etc.
(1.2, 1.8, 2.5 are 1/4 stop under the next whole stop; 3.5 is 1/3 stop
under 4; 4.5 is 1/3 over 4; etc.) Would anyone like to contribute the
1/4 and 1/3 stop sequences?
Hope This Helps