Graflex.org

[AaronC]

Listed below are the focal plane shutter speeds of 2 Anniversary models I have.

Indicated 4x5 3.25x4.25

A1 1/10 1/28 1/26
A6 1/40 1/39 1/40
B1 1/70 1/104 1/118
B6 1/150 1/126 1/155
C1 1/200 1/135 1/295
C6 1/400 1/421 1/386
D1 1/500 1/645 1/621
D6 1/1000 1/757 1/704

The 4x5 has been heavily used. The 3.25x4.25 very little. It's interesting the speeds are so close. Perhaps these cameras had this pattern when new, or the springs “age” the same.

My experience is that these cameras reach an upper speed limit- any tightening of the spring after this increases the lower shutter speeds with little effect on the top speed. However, I haven’t really pushed the upper limits because I’m cautious with mechanical things. I don’t want to break what I have.

For these values I took 5 readings at each setting and averaged them. I previously had done trials with 10-15 tests per speed. Each shutter fired consistently within 5-20% of the averaged value.

The measurements were taken using an infrared photo diode, some electronic circuitry and an old frequency meter. The set up is accurate to 1/100,000 second. The diode was placed in the middle of the 4x5 frame.

AC

[Sjixxxy]

Well. I got a calumet unit and just wrecked my wrist cocking that blasted shutter on my Anniversery 240 times to take ten readings at each of the 24 different settings. Here are my results.



Just as I suspected, the A1 setting was a bit faster then labeled. Though my guess was that it was going to be 1/30th. D6's accuracy was a bit suprizing. I'm guessing someone in the past jacked up the tension spring a bit. Now I need to print this off, laminate it, and take it with me when I shoot.

And because they are fun, a graph!




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Zeropoint

[ This Message was edited by: Sjixxxy on 2005-01-11 17:36 ]

[ This Message was edited by: sjixxxy on 2005-01-12 00:15 ]

[Joe Koski]

Very interesting results, which bring to mind some more questions. For example, what was the camera-to-camera variability as manufactured and after use in the 40s? In most cases, the results are within an f-stop (factor of 2) of the correct value. The shutters haven't slowed down as much as I have, and I'm about the same age.

Joe

[Sjixxxy]