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[OM] Re: Depth of field calculator

Subject: [OM] Re: Depth of field calculator
From: "Piers Hemy" <piers@xxxxxxxx>
Date: Wed, 22 Jun 2005 18:02:12 +0100
I don't doubt any of that AG - at all.  Interesting especially is your
description of the OOF characteristics (or perhaps "not-as-much OOF").

And permit me to praise your use of words to describe the optical behaviour
in such an easy-to-grasp manner - I find it immensely difficulty to explain
such things in words, without the benefit of pictures/diagrams.

I suspect that all we can deduce about 4/3 lenses from the spreadsheet is
that there is more DoF than we need, but what you seem to be saying is that
the distinction between in-focus and out-of-focus portions of the image is
plainer with non-digital lenses than with a tele-centric ZD lens?  I assume
you are using both on a digital body.  Have I got it right?

What is CoF?  CoC in another guise?

--
Piers 
 
-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of AG Schnozz
Sent: 22 June 2005 17:52
To: olympus@xxxxxxxxxx
Subject: [OM] Re: Depth of field calculator

I built a set of tables for the 2/3" sensor on my site.  I've been planning
on doing the same for 4/3" sensor.  However, I haven't quite come to grips
with the CoF as the commonly used CoF for 4/3 isn't quite matching what I
want to see.

Another factor about modern telecentric lens designs is that the bokeh
characteristics aren't linear as you'd find in a 40/2, 35/2.8, 85/2 or
100/2.8. The 14-54 ZD lens, for instance, has an apparant "zone of in-focus"
whereas a traditional lens has a "plane of in-focus". In a traditional lens,
an OOF highlight will continue to expand and dim the farther out of focus it
becomes. With a modern lens, an OOF highlight will expand a smaller amount
and will tend to stay just as bright.  The "goal"
among many lens designers is to create a deep-focus lens by getting
perfectly telecentric "rays".

In otherwords, the DoF tables for 4/3 isn't quite as straightforward as we
think.

AG




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