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Re: [OM] OM macro / closeups vs medium format / TLR

Subject: Re: [OM] OM macro / closeups vs medium format / TLR
From: frieder.faig@xxxxxxxxxxxxxxxxxxxxxxxxx
Date: Fri, 4 Jan 2002 13:54:26 +0100
On Fri, Jan 04, 2002 at 12:19:09AM +0000, John A. Lind wrote:
> At 13:45 1/3/02, Frieder Faig wrote (in part):
> >Good site. Must have been lot of work. I like it.
> 
> Surprised you didn't mention my page is missing the equations that were 
> used.  Thought about that after I uploaded it.  I should have put them on 
> the page (so anyone can replicate the graphs).

Oh, I forgot I wanted to mail you this:

You`ve been locking for information about the acceptable size of the circle of 
confusion(coc).
You`re reseach in literature ended up with the usual values, aceppted in most 
sources I know.
Here are some intresting toughts:

When you wan`t more dof, you`ve to sacrifice maximum sharpness:
        smaler apperture -> more diffraction
        smaler film format -> ...
        accept more coc -> ...

Now Zeiss seems to accet less coc...
I´ve read an article where the autor suggests to use the coc dependung on your
demand of quality.  It also changed during history of 35mm photography (better 
films...)

Now the point: the resolution of human eyesight?
An optic book give the following values:

(1) 1 arc minute ( 0°01'00") to differentiate two points ( best resolution when 
diameter
of your eyes-pupill is 2mm!). This value is relevant for dof considerations.
Equals ~73 µm in 250mm viewingdistance.
(2) For "vernier read of" your eye can detect up to ~18µm in 250mm distance 
(caliper).
(3) And for "symetric read of" your eye can detect ~ 6µm in 250mm distance 
(OM1-needle!).

I´ve made a test with a resolution chart: Which re the finest lines I can see. 
I ended up with a value slightly better than (1). which were 0°0'53". Which 
correspondent to my 
opticican who said: "with glasses I´d see 120%"

>From this starting point, it is easy to calcualte the max. value for coc,  
>depending on the
size of your "photograph" and the viewing distance. 

Frieder Faig


> 
> -- John
> 
> 
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