Re: Aperture calculations; 6.3 or 6.7???

[P3D Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

It appears that the series of apertures:

1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44...

is a geometric progression where every term is derived by multiplying
the previous one by the square root of 2 which is 1.414...

Also, every term is equal to the square root of the product of the
neighboring terms, e.g. 8 is approx. the square root of 5.6 x 11.

In between half-stops are derived, I believe, by multiplying the previous
term by the square root of 1.414... which is 1.19... or by taking the
square root of two neighboring numbers.

Thus, the half f-stop between 5.6 and 8 is either 5.6 x 1.19 or
sqrt (5.6 x 8).  Both methods give 6.7.  So, why is it assumed that 
6.3 is the f-stop half way between 5.6 and 8????

George 


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