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Re: [OM] Fast Wide Angles

Subject: Re: [OM] Fast Wide Angles
From: "Paul D. Farrar" <farrar@xxxxxxxxxxxx>
Date: Fri, 26 Mar 1999 20:45:38 -0600
At 03:41 PM 3/26/99 EST, you wrote:
>In a message dated 3/26/99 3:28:32 PM EST, farrar@xxxxxxxxxxxx writes:
>
><< For those who just have to know:
> 
> Let SN = 1 when square N is shiny, SN = 0 when not
> 
> S1 is always 1
> A = S2 + 2*S3 + 4*S4
> B = S5 + 2*S6
> 
> ISO = 25*2**A + (2**(1/3))*(B-1)
> 
> Notice that this scheme helps with cheapo cameras.
> You can detect the multiples of 25 by sensing three squares.
> 100, 200, 400, and 800 by sensing 2 (S2 & S4).
> And for real cheapos, decide between 100 and 400 by sensing only S4.
> 
> Paul
>  >>
>Paul,  
>       I assume this explains how to do exposure compensation for DX only 
> cameras?
>       Maybe I'm thick headed, but I don't follow what the above means. Could 
> you
>       possibly explain it more? Maybe type it a little slower !  :)
>
>Thanks
>George S.

Here's the table typed out. You need a monospaced font.

ISO  123456
  25 *   * 
  32 *    *
  40 *   **
  50 **  * 
  64 **   *
  80 **  **
 100 * * * 
 125 * *  *
 160 * * **
 200 *** * 
 250 ***  *
 320 *** **
 400 *  **
 500 *  * *
 640 *  ***
 800 ** **
etc
1600 * ***
etc
3200 *****
etc
5000 ******

The second row uses square 7 for ground, 8-10 for number of frames, and
11&12 for latitude. (I've never seen a camera use those last two.)


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