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[OM] Re: Depth of field calculator

Subject: [OM] Re: Depth of field calculator
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Wed, 22 Jun 2005 19:59:32 -0400
Are you sure that this isn't simply that the "plane" of focus isn't flat 
but is a curve instead?  I think most non-macro lenses exhibit some 
curvature in the plane of focus.  Are the ZD's just more-so in this 
respect or is there truly something else going on?

Chuck Norcutt

AG Schnozz wrote:


> 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.




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