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From:  "Jaye" <jaye@sasaudio.com>
Date:  Thu Jun 24, 2004  8:12 pm
Subject:  RE: [ACG] Shutter adjusting [tech tip] really

Henry,

Very good question about adjusting the C3 speed.

I have pondered this for a long time and can provide to following suggestions;

You stated 'reasonable accuracy'. In most old cameras the highest speed is unrestrained and with reasonably clean shutter-works that is simply whatever the shutter runs at. often it is within 20% of the indicated speed and almost always on the 'slow' side.

The slowest speed uses various tricks to achieve but in all vintage models of the Argus, except the 75, a 'clockwork escapement' is used. In the C3 this has a specific adjustment device located on the front, hidden underneath the leatherette at the 4 O'clock  position relative to the lens. The access hole is a bit smaller than a Dime (U.S. coin ~ 12mm or 1/2") and has a brass disc cover (occasionally missing).

The actual adjustment is a screw and nut that holds a 'bell-crank' (slightly
triangular meter device).

Now, last time I stated this backward so who knows what my memory will come up with now. 'To adjust the slow speed you loosen the screw a fraction then turn the nut then re-tighten the screw'.

Did I get that correct?

The real trick is how to determine the correct speed.

Again you said reasonable. Here is what I do and occasionally I verify using an home made instrument to show that it does work:

I listen to one or two modern cameras set for 1/10 or 1/20, and again at 1/125 or 1/100 to learn the sound of the shutter 'time' then check the sound of the C3. The human ear is far faster than the eye and can perceive the difference between 1/20 and 1/10 easily and with a bit of care you can sense the difference
of 1/125 versus 1/100.

More complex tricks are:

Drop a ball with some measuring scale in the background, shoot at 1/10 or 1/20 then run the math against the blurred image of the ball and the distance traveled.

Take a picture of a record player turntable (not many still around) spinning a sheet of paper with marks on it and then, run the math based on speed, diameter etc. converted to inches per second.

Take a picture of a car passing by and, run the math on the length of the blurred image versus speed of the car.

The ear is simple, the math is not hard but you need to recall simple physics learned decades ago and the ear is usually quite handy to operate.

Thank you.

Jaye

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From:  "Richard T. Reeder" <r.reeder2@juno.com>
Date:  Sun Jun 27, 2004  4:20 pm
Subject:  Shutter adjusting [tech tip]

Concerning C3 shutter adjustment:

I used a 3/16 socket, ¼ inch drive, and a small blade screwdriver. The
screwdriver fits down through the hole in the socket. I was able to put this 'assembly' through the access hole, unlock the screw by turning the screwdriver counterclockwise (CCW) (it's a right hand thread, RHT) while holding the nut still via the socket, then adjust the nut with the socket, and then lock the screw by turning the screwdriver clockwise (CW) while holding the nut still via the socket.

I've got in my notes that when the screw is at the 12 o'clock position,
the shutter speeds get speeded up; when the screw is at the 6 o'clock
position, the shutter speeds get slowed down; when the screw is at the 3 o'clock position, the faster speeds get affected; when the screw is at the 9 o'clock position, the slower speeds get affected.

Of course, the screw can be at any position, not just these 4, and the
result is a combination of effects.

There is a pivot point under the triangular bell crank, and the pivot
position is the opposite of the screw position. In other words, when the screw is at the 12 o'clock position, the pivot is at the 6 o'clock position.

And, our resident Shutter Guru, Jaye, has mentioned: "In each C3 the
screw-slot is at a random position relative to any other C3 set for the
same speed. Many reasons but that is the end result.

Now, the fact is that you cannot adjust the 'Fast' independently of the 'Slow' speed through adjusting the bell-crank under discussion. The
escapement/timer gears are very simple and you can only affect the
over-all speed.

If you were to adjust the bell-crank to cause the escapement to run
abnormally slow then the high-speed would be affected because the actual
internal setting would be so shifted from the desired position that the
highest speed would never be 'dialed-up' via the speed setting dial.

On the other hand if you adjust the bell-crank to cause the slow speed to run abnormally fast then the highest speed would occur before the dial setting was turned to the fastest position.

I have seen the highest speed (1/300) occur when the dial is at 1/100 if the bell-crank is set completely wrong. I mention this to give a feel for the range effects.

The Linearity of this adjustment is only affected by two parts. The Cam
located behind the speed dial and the location of the 'Rod' attachment
holes on the bell-crank. The escapement is not adjustable. The
return/shutter spring affects the over-all speed." (Message 7, Digest #175; subject: RE: Shutter adjusting [tech tip] really (2nd & 1/2 try.))

All of the above is true.

I love the C3 for it's maintenance friendly construction.

Rich Reeder, 1320.SUN.27.JUN.2004 (MST), r.reeder2@juno.com
Mesa, Arizona