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[OM] Re: DOF question

Subject: [OM] Re: DOF question
From: "Piers Hemy" <piers@xxxxxxxx>
Date: Fri, 27 Apr 2007 09:42:04 +0100
DoF as a topic is one that has been explored here before, and my conclusion
is that it is a topic unsuited to discussion in a text-only discussion forum
- so I didn't ignore it, I did my best to avoid it!  And not because it's a
dumb question, but because the way you phrased it suggests that there is a
simple, objective answer. I think the responses you had already received
were as good as anybody could give - but then Chuck came up with his
masterpiece.  

I won't try to cap that, but I will offer the following further references:

A Depth of Field calculator from Jonathan Sachs (Picture Window Pro
developer) http://dl-c.com/Temp/downloads/DOF%20Calculator/Default.htm which
has the following as the first line of the help file: "Depth of field does
not depend on the frame size (e.g. 35mm, 6x7cm, digital camera CCD,.)."  The
help file alone is worth the price (OK, it's freeware)

"The Ins and Outs of Focus" a freely downloadable book by Harold Merklinger,
which goes into some depth (oops) about the topic
http://www.trenholm.org/hmmerk/TIAOOFe.pdf

And I will also offer my personal suspicion that the best 35mm lenses can
resolve better than the lens DoF marking convention assumes - as Jonathan
Sachs says "a standard value of about 30 lines per mm is often used to
compute depth of field markings on 35mm lenses".  The result would be
apparently shallower DoF than the lens markings indicate - and the DoF
calculator will allow you to play with the numbers to see the effect.

--
Piers 
      

-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of Ali Shah
Sent: 27 April 2007 02:27
To: olympus@xxxxxxxxxx
Subject: [OM] Re: DOF question


Thanks. 

Why is my DOF question being ignored? Is it an overly dumb question? Perhpas
the simple answer is the smaller sensor which cant absorb as much?!?

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