Seiko #0 shutter Measuring shutter times (Rev 2)

Measuring Seiko #0 shutter times (Rev 2)

By M.Vettore

Every Zenzanon lens for ETR, SQ and GS camera families has embedded its Seiko #0 central (leaf) shutter;
the outcome is large part of the shooting process depends on lens while on the focal plane shutter cameras
the lens has little relevance on the shooting phase usually it only sets the diagraph at the chosen aperture.
Because of that, verify the health of a focal plane shutter camera lens is quite simple, check Zenzanon lenses
not.
To test this kind of lens a shutter speed meter is needed. Further than an expansive professional meter it is
possible to build a cheap shutter speed meter utilizing the microphone input of the PC sound card. For the
details refer to:

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=0044cW&tag=

or

http://www.baytan.org/prak/shutter.html

I’ve built one of these and it is enough accurate to test the lens but a little complex to use, indeed it is
necessary to arrange in a line the shutter meter, the camera without back and the light source; cock the
camera, arm the program used to perform the measure then shot, better using a shutter release cable. By the
way it is practically impossible to test a lens without the camera body or a bare bone shutter at theirs default
time

PIC 1: Measuring times through the lens.

I’ve found a simpler way to test the lenses.
As I stated on another document ( http://www.buonaluce.com/Anatomy ) the flash sync contact is driven by
the same ring actuating the shutter leaves so the flash sync contact will be closed when the shutter is almost
full open and will be opened when the shutter is closing. Using this feature it is possible to realize a very
simple shutter tester taking advantage of the PC audio board. This simple tester can check the shutter at any
speed and also lenses detached from camera body and bare bone shutters at their default time (1/500 of
second).

S

SW1

C1

C2

R1

B1

P1

W1

R2

Schematic diagram of the shutter tester:

+

Components list
S1 Mono jack socket 3.5mm
SW1 Normally open pushbutton (optional)
C1 47 nF 50V capacitor
C2 4.7 nF 50V capacitor
R1 820 ohm 1/8 W resistor
R2 1200 ohm 1/8 W resistor
B1 1.5 Volts AAA or AA battery
P1 Mono jack plug 3.5mm
W1 Audio shielded cable

The circuit is very simple and can be assembled on a small case; by the way it doesn’t require any on/off
switch because it drains noticeable power only when the flash sync contact is closed.
It could be connected to the Flash X synch socket using a cable terminated with a standard PC plug on one
side and a 3.5mm jack plug on the other.
The pushbutton isn’t necessary but it is very useful to verify the circuit works fine and eventually to calibrate
the acquisition program.

Layout sketch

As acquisition program I use the excellent Soundcard Oscilloscope by Christian Zeitnitz available at:

http://www.zeitnitz.de/Christian/Scope/Scope_en.html but any other acquisition application capable of

measuring time intervals should be useful.