P3D Re: Hyperfocal Tables

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

Dr.T writes;
>Thank you Gabriel!  You just wasted 15 minutes of my valuable time! :-)
>Here is what you wrote in Digest 2578:

Mission accomplished! ;-) BUT now your getting even with me and wasting
30 minutes of my time! Your keeping me way past my bedtime! -) zzzzzzz

I wrote in digest 2578;
>>wondered why there were differing tables and the conclusion was 
>>because the CoC parameter was probably changed. 
                                ^^^^^^^^

Dr.T replies;
>That's no mystery solving... It is just a guess.  A guess that
>turns out to be correct :-).  But I confirmed that this is inddded
>the case from offical Realist documentation.  So, *I* solved the
>mystery! :-)

No, no, no, it wasn't a guess! In that specific post I was RECAPING
about how it was a guess UP TO that point in time! In that same post,
the mystery is subsequently solved by proving it was indeed the case
that the CoC was changed! See supporting documentation below from
post in digest 2578, dated Feb.12, 1998. ;-)

-----------------SUPPORTING DOCUMENTATION----------------------

Different CoC are used to reflect if it's a slide, small print,
large print, etc. and consequently yields different tables. But
this begs the question, why did they change the table (since
slides were used in each case)? Was it to fudge the performance
or was it a reflection of better lenses, film, etc.?

On an Realist with Ilex lenses and another Realist with David
White lenses I found these two differing tables.

David White f3.5 lenses
Hyperfocal Table (serial number A55495)
---------------------------------------------
Diaphragm    Set Distance  Camera is in focus  
 Setting        Dial On         From   To 
   f2.8           44'            22'-inf.
   f3.5           34'            17'-inf.
   f4             30'            15'-inf.
   f5.6           22'            11'-inf.
   f8             15'           7.5'-inf.     
   f11            11'           5.5'-inf.
   f16             8'             4'-inf.
   f22           5.5'          2.75'-inf.

Ilex f3.5 lenses
Hyperfocal Table (serial number A8314)
---------------------------------------------
Diaphragm    Set Distance  Camera is in focus  
 Setting        Dial On         From   To 
   f3.5           45'            22'-inf.
   f4             40'            20'-inf.
   f5.6           28'            14'-inf.
   f8             20'            10'-inf.
   f11            14'             7'-inf.
   f16            10'             5'-inf.
   f22             7'           3.5'-inf.

>From the two tables above, it looks like the CoC was increased
for the DW lenses but I wasn't sure by how much.

Refering to the formulas given in the handbook, the hyperfocal 
formula is given by,

        F x F
H = -------------
     (f x C x 12)

where H, hyperfocal distance (feet)
      F, focal length of lens (inch), (35.2mm=1.3858inch for a Realist)
      f, aperture (f/number)
      C, circle of confusion (inch)

 
Solving for C, the Ilex lenses results in a CoC (C) of 1/1000
(.001 inch) of an inch. Later with the DW lenses they increased
the CoC to 1/750 (.00133 inch) of an inch.

---------------END OF SUPPORTING DOCUMENTATION-----------------

NOTE the last paragraph which breaks the case! 

I wrote;
>>Now one would think that they would decrease the CoC for the DW
>>lenses, since they are supposedly not as sharp as Ilex lenses but
>>we see the opposite. From all this it would seem to indicate that
>>it was done for purely marketing purposes.

Dr.T writes;
>The only considerations in selecting a value for this "circle of
>confusion" are the resolution of the film and the viewing conditions.  
>Not the lenses of the camera but the lenses of the viewer!  So it 
>would make sense to say that they reduced the circle of confusion 
>because they now use lousy lenses in the red button viewers! 

I agree that technically, on the considerations for selecting a CoC, but
I still think it was changed for a non-technical reasons (marketing!).
I suspect they changed it because of competition from Kodak!

>I am quoting from "Realist News 1.4 (Oct.1951):
>
>"The Hyperfocal Table figures quoted in this article indicate 
>somewhat greater range of sharpness shown on the table on the
>camera.  The new table is calcuated using a 'circle of confusion'
>of 1/1000 of an inch.  The new table is calculated using a
>figure of 1/750 inch and is more than sufficient for any stereo
>viewer."  (Shortly after this the Tables were changed in the cameras)
>^^^^^^

Assuming any of what they wrote is true, they do mention ANY viewer.
Therefore how does this impact on those that used the now larger CoC
with the older "better" lenses? Would they have noticed it? I 
suspect not. 

A few months after my original post, I did by a copy of the
newsletters from Dalia and noticed this reference but by then the
thread was old and didn't bother posting it and besides it didn't
shed any new insight from what I originally posted.

P.S. It's okay Dr.T, like they say, everything in 3-D has been
     done and said already, and in this case was probably solved
     (or actually solved) along time ago, before any of us! ;-)

P.P.S. Please reserve a copy of your new book for me!
     
Gabriel


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