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[OM] 38mm macro and focus screens

Subject: [OM] 38mm macro and focus screens
From: usher99@xxxxxxx
Date: Tue, 23 Feb 2010 08:05:13 -0500
Hmm,
A Dr. Florida now---I bet he as as astute as the renowned  but 
reclusive Dr. Focus and the
esteemed  list treasure, Dr. Flash.

I suppose focal length will effect magnification on the same extension 
but I was trying to assess the effect of magnification per se
on the ability of tilt to move the plane of focus.  Most of the 
calculators I have seen assume thin lens approximations and
fall apart with higher magnification.  Longer FL seems to reduce the 
effect of tilt  on moving the near and far plane of acceptable focus.
My first attempts with the Mirex with landscapes was plagued by 
over-tilting as I did realize how little was required.  I now have an 
excel
spreadsheet with FL and tripod height.  I think only 2 deg is required 
for a 45mm lens at my eye level tripod height.

http://www.cambridgeincolour.com/tutorials/tilt-shift-lenses2.htm

I really have no clue if magnification per se----( i.e.  shortest 
extension using the 38macro  on the autotube with 8 deg tilt  vs 
longest extension)
has on the ability of tilt to shift the plane of focus.  Perhaps very 
little though total dof and ?angular dof will decrease.

Mike




How do you distinguish between "longer focal length" and
"magnification".  To me they go hand in hand... or didn't I understand
your point.

Dr. Florida


usher99@xxxxxxx wrote:
> Thank you Ed and Don for your comments.    Longer focal length
> diminishes  the effect of tilt   on shifting the plane of focus.  I
> have no clue if magnification has any effect  on this though the 
total
> angular  dof  I suspect  may diminish.  Wonder if Dr. Focus is in 
Fla.
>   It would be nice to see this effect in the VF, but if the subject 
is
> not properly focused, all is lost anyway.  The 1-12 is weird-- 
largely
> clear but doesn't alter metering.
> Sometimes wish I could swap screens with a dial.
> Mike
-- 
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