[ATM] RE: [atm_free] zone one challenge

["Jerry" <wa4guu@verizon.net>]

If you look at the images closely you will see that what you are seeing is
something similar to the classical "doughnut"  in each mask opening.
separately.  A doughnut, except that it is an arc. Your simulation seems to
be showing "nulls" either side of center in each mask opening. Therefore the
center of each of the openings is not the same as the average intensity. The
average is located a little to the left and right of center in both mask
openings.

 

I'm thinking that the doughnut made into an arc is an artifact of the
simulation method. Maybe, maybe not, but the shadows are showing a doughnut
profile in each opening. So I'm thinking an opening was simulated on its own
and somehow a doughnut like profile generated. Then that profile extended
around the arc of the zone opening.

 

But the left and right openings do have a symmetry in their appearance. Look
at simulation J, The right opening  has a central area (center of the mask
opening) that is light bounded on both sides by darker shades and on the
left it is dark in the center and lighter to either side. Now the central
band in each opening maybe is not the same intensity, but the center of
symmetry in each opening is at the center of the mask openings. If that is
not an artifact it may say something about the method of looking for
simultaneous change in intensity in left and right openings when jogging the
knife laterally across the slit image. 

 

I suspect that the shadow contrast in the simulation is exaggerated. That
can be hard to simulate when you don't know how I have my monitor adjusted.
What is the radius on the mask of the outer edge of the opening?

 

Jerry 

 

  

 

-----Original Message-----
From: Koehler, Steve [mailto:steve_koehler@securecomputing.com] 
Sent: Wednesday, March 30, 2005 10:47 AM
To: atm_free@yahoogroups.com; atm@atmlist.net
Subject: [atm_free] zone one challenge

 

I believe I have found a possible source of bias in reading zone one in an
8-zone test of an 18" f/4.5.  I have written up my ideas in the following
report, which includes a challenge to find the null for zone one from a
series
of 15 simulated images.

    http://www.visi.com/~mkoehler/zoneone/zoneone.html

As I mention in the report, I would like to hear from anyone who gets the
right
null the first time.  What technique did you use?  Please don't inundate the
lists with reports of your answers, especially if they follow my prediction
that
most people will read about .004" inside the proper null.

-- Steve Koehler
   steve_koehler@securecomputing.com







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