[rollei_list] Re: Spinning front taking lens
- From: Don Williams <dwilli10@xxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 29 Dec 2005 10:36:41 -0800
At 09:33 AM 12/29/2005 -0800, Jim Brick wrote:
I'm not sure that I understand this lens spinning property.
I have always been told that in lenses that consist of more than one
element, each element has a specific orientation with the other
elements in the group. I was told that if I took a lens apart, I
should mark each elements orientation so that it could be
reassembled with each element oriented properly with respect to the
So a spinning element makes no sense to me.
The curvature on the "true" front is generally different from that of
the "true" back. Even though I know this, when I recently cleaned a
projector lens, I thought I would remember the direction each element
belonged, so I didn't mark the elements, which were free-floating,
with plastic spacer rings in between them. There were only 3
elements in the lens but the front-to-back orientation of a couple of
them wasn't obvious by inspection so I had to try various
combinations until the lens presented a good image.
Actually, due to the design of this lens, once the screw ring was
removed the elements could tumble as the came out, so maybe that's
why I didn't mark them.
Maybe the orientation you have in mind is front vs back for the elements.
La Jolla, CA
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