[rollei_list] Re: Hearing Aid Batteries in Nikon F
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Wed, 3 Mar 2010 21:56:48 -0800
----- Original Message -----
From: <stephen@xxxxxxxxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Wednesday, March 03, 2010 3:07 PM
Subject: [rollei_list] Re: Hearing Aid Batteries in Nikon F
I notice about a 1/3 stop difference between a discharged
silver cell and a 'full' one in my converted Nikkormat.
Solution: replace the silver cell before using the camera
for critical work.
While folks in the late 90s got into differences of 1/6 of a
stop with their digital wonder meters, the old Modern and
Pop Photo magazines in the Oakland Public library used +-
1/2 stop from a reference light source as their standard. A
bit of tolerance certainly makes life a bit easier...
...and which of you keep a shutter speed tester, measure
your actual shutter speeds and keep them on a card in your
camera case for reference? (I believe Bill Pierce used to do
that with his Leicas). As I recall, the tolerance for
mechanical shutters was 1/3 of a stop, 1/2 stop for the
highest two speeds.
The tolerance of Compur shutters was +/- 20 percent, at
least at the highest speeds. Note that the marked speeds on
nearly all shutters is the _effective_ speed when the iris
is wide open. That takes into account the error due to lack
of efficiency. The effective speed is larger for smaller
stops. If you measure a Compur at full speed (1/500th for
modern ones) the speed on a meter which measures only the
center of the beam, i.e., total open time, is about 1/380th.
The marked speed becomes closer to the effective speed for
slower shutter speeds because the opening and closing time
of the blades remains constant at all speeds.
For the most part positive-negative systems both B&W and
color have a pretty wide tolerance for exposure error but
reversal films of both types are quite critical.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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