[rollei_list] Glass plate and focus shift, an academic question ;-)

  • From: Bigler Emmanuel <bigler@xxxxxxxx>
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Thu, 27 Sep 2012 18:32:34 +0200


John says :

John explained perfectly the practical issues regarding dust on the
Rolleiflex "film-flattening" glass plate.

Regarding focus shift, yes, there is one, but this is no problem at
all, since the plane glass fixture was cleverly designed by F&H to
compensate for it, as explained of this schematic drawing:

http://farm4.staticflickr.com/3411/4573709647_e2452f3150_z.jpg

We could add that Chris Perez measured resolution limits in excess of
of 90 cy/mm on a freshly adjusted Rolleiflex TLR (planar or xenotar
2.8-80), with the infamous 120 rollfilm & its infamous backing paper,
with no flattening glass at all:
http://www.hevanet.com/cperez/MF_testing.html

"The theory is great but in practice, ..."
my answer is, as usual:
"If theory disagrees with practice, it is because most often, practice
is plain wrong"

--
Emmanuel
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