FW: [ATM] zone one challenge

["Koehler, Steve" <Steve_Koehler@securecomputing.com>]

[I'm resending.  I accidentally sent it just to Mike.]

Mike,

> Actually, I think your page also demonstrates quite well the problems
> with reading zones that are too wide and the problems that can result.
>   If this were my mask, I would probably have made a new one with two
> zones instead of the one wide one.  

This is probably the proper fix to this problem.  When I tested my 18" f/4.5 I
used nine zones.  For the simulation I took the suggested number of zones from
Nils Olof's zone calculator (7.7 zones), and rounded it up to 8 zones.  Perhaps
this means that strictly equal area zones is not quite the correct formula for
the innermost zone, or two.  When I get around to retesting my mirror, I will
make narrower inner zones.

> PS: I chose "I", 0.002" inside the proper null.

Very good!

-- Steve Koehler
   steve_koehler@securecomputing.com


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