[rollei_list] Re: Rolleiflex 35 SL lenses QBM IV (3-Pin)
- From: John Wild <JWild@xxxxxxxxxxxxxxxxxxxxxx>
- To: "'rollei_list@xxxxxxxxxxxxx'" <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 21 Aug 2010 11:29:32 +0100
James,
I am sure you will experience 'the wrath of the gods' for posting images on the
list ;-) but, yes the recessed ring with the two spanner key slots in it. The
depth of that ring determines the maximum aperture of the lens which the camera
picks up...
I have measured my lenses, using the matt step of the mount - assuming this is
the reference register face - to the bottom of the groove using a digital
vernier caliper. A dial gauge would be more accurate but there should be a
reasonable tolerence and I expect that the depth when plotted on a graph will
be linear, so discrepencies can be adjusted...
F1.4 - 1.15mm
F1.8 - 1.4mm
F2.8 - 1.9mm
F4.0 - 2.2mm
An earlier QBM has no step at all which gives the camera a 'no maximum aperture
available' signal, but the 'aperture set' information is still transferred to
the camera by the 'finger' on the lens.
John
-----Original Message-----
From: rollei_list-bounce@xxxxxxxxxxxxx
[mailto:rollei_list-bounce@xxxxxxxxxxxxx] On Behalf Of James Richard Tyrer
Sent: 21 August 2010 01:37
To: rollei_list@xxxxxxxxxxxxx
Subject: [rollei_list] Re: Rolleiflex 35 SL lenses QBM IV (3-Pin)
On 08/10/10 04:33, John Wild wrote:
> James,
>
> Belatedly responding to your query; from memory (I do not have any of
> my 3000 lenses in front of me), the QBM IV lenses have a groove around
> the circumference of the mount. The groove depth gives the maximum
> lens aperture information to the camera metering system.
John:
I think that I now understand this enough so that if I had a lens in hand and
armed with a caliper that I could tell a QBM III from a QBM IV.
Still looking at pictures and trying to figure out what to look for in a photo.
That attached photo shows the outer retaining ring on the rear of a Planar
50/1.8. Is that small step in the retaining ring what I should be looking for?
--
James Tyrer
Linux (mostly) From Scratch
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