[rollei_list] Re: Rolleiflex FT focusing mechanism
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Wed, 27 Oct 2010 12:27:18 -0700
----- Original Message -----
From: "Eric Goldstein" <egoldste@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Wednesday, October 27, 2010 6:02 AM
Subject: [rollei_list] Re: Rolleiflex FT focusing mechanism
On Wed, Oct 27, 2010 at 8:52 AM, CarlosMFreaza wrote:
(snipped)
I really thought
that the 1,5m nearest focusing distance was obtained via
the new lens
optical formula mainly thanks to some powerful elements
combo as
commented in some forums and with some slight
modifications for the
focusing parts.
Hi Carlos -
How would this be possible?
Eric Goldstein
I don't think it is and Carlos changes this in his
later post. While its possible to change the back focus of a
lens, that is the distance from the back of the lens to the
image at infinity focus, by optical means the distance the
lens must move to focus for a closer object remains the same
for a telephoto or reversed telephoto lens as it is for a
normal lens.
One change that seems to have been made in all later
Rolleis is the method of supporting the front standard.
Later cameras have tubular posts and other differerences
that would result in much better parallelism and stability.
This would be necessary to maintain the axial centering of
the lens to the film plane when the travel of the front is
increased as it must be for a longer focus lens. I am not
sure how the additional travel was obtained but the focus
mechanism uses a combination of cams to move the front. In
order to move the front further the size of the cams must be
increased or levers must be employed. There are no levers in
the mechanism to I think Rollei must have used larger cams.
That would have required other changes in the layout in
order to accomodate them.
This also makes me curious about the lenses used on the
WA Rollei. Are they retrofocus types, I have not looked yet.
If not then the lenses must be moved in toward the film. The
range of "bellows draw" could remain the same for a WA lens,
it would just be able to focus closer than the standard
lens, so the same cams could be used as in the standard
version.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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