Changing Shutter Speeds in Charged Copal Shutters: Fact & Fictiongreenspun.com : LUSENET : Large format photography : One Thread
Let me share a recent exchange with S.K. Grimes (SK). I was contacting Mr. Grimes about some custom lens caps that I am ordering for my Schneider LF lenses when we got on the subject of Copal shutters: (reprinted with his kind permission -- thanks!): -- Paul Chaplo (PC)
PC: After hearing that it is detrimental to change shutter speeds after a Copal shutter is cocked, I have refrained from doing so. Can you confirm that this is true? SK: Quoting from the Copal instruction book, packed with new shutters: "Charging the shutter, opening or closing the shutter blades, changing the shutter speed, changing the aperture stop....all these things can be manipulated in any order you like without the least ill effect on the shutter mechanism." I have always interpreted this as having it be OK to change the speed with the shutter cocked. PC: What happens when an uninformed person does so? SK: He risks getting balled out by another uninformed person. :-) This whole thing is a little like keeping your foot on the clutch with the gear shift in low gear while waiting for a traffic light. It won't hurt a car in good condition although arguably its better to shift to neutral and take one's foot off the clutch while waiting for the light to change. But not enough better to change someone elses behavior about.
-- Paul Chaplo (firstname.lastname@example.org), October 29, 2001
Thanks, Paul. As a LF newbie, I was curious about this. Thanks to you and SK, not anymore.
-- Tony Karnezis (email@example.com), October 29, 2001.
I must register my disagreement with this statement. Leaving the gear shift in neutral while at a stop light leaves one in a position less able to react quickly if necessary.
Now, what are those dangerous little buzzing and whirring sounds when changing shutter speeds after cocking the shutter?
~chris jordan, Seattle
-- chris jordan (firstname.lastname@example.org), October 29, 2001.
Awlright, I'll have to chime in now.
Actually, it IS better to put the car in neutral. There is a matter of the throw out bearing to consider with manual transmissions. It will last longer if you routinely put the transmission in neutral rather than keeping the clutch disengaged.
That being said, it's true, the reaction time is severly limited by doing this and I usually don't put mine in neutral except when I'm going to be stopped for a while, like a long light or heavy traffic.
Last clutch lasted 95k miles (not too bad) considering I didn't baby it.
-- S Ratzlaff (email@example.com), October 29, 2001.
Chris: Those buzzing noises are the gears in the speed train winding down or up as you change shutter speed. They're just the normal noise that the gear train makes, and not at all 'dangerous'.
I'm sure that Steve Grimes has had enough shutters apart to see what happens when the shutter speed is changed. I'm also confident that an experienced engineer like Mr Grimes is perfectly capable of assessing whether such movement is detrimental to the mechanism, or not.
When this is further backed up by Copal's statement; then I think that you can take it as read that changing the shutter speed on a Copal shutter, cocked or uncocked, will not harm the mechanism.
I've had a few shutters apart myself over the years, and I can further confirm that all that changing the speed does is to engage or disengage a train of gears from the speed retarding mechanism.
The only thing I can add is that setting the delayed action to 'v' with the shutter cocked may be detrimental to some shutter designs, that's all.
-- Pete Andrews (firstname.lastname@example.org), October 30, 2001.
How does a throw-out bearing that is being held motionless wear out? Pushing the clutch in and out twice to put the car in neutral and take it back out would wear the bearing twice as much as pushing it in once and holding it.
I've never heard of putting the car in neutral while at a stop.
-- John H. Henderson (email@example.com), October 30, 2001.
Finally something I can positively contribute to this forum. Unfortunately it has nothing to do with photography.
The throw-out bearing is only in motion when the clutch is pushed in. This is obviously a very brief period of time when actively shifting but if you sit at a light with your foot on the clutch you are causing magnitudes greater usage and wear. The labor cost for replacing this baby are the same as for the entire clutch. Also, what if you need to go backward for this anticipated emergency evasive manuever?
Apologies for prolonging this thread but I couldn't resist an area that I actually know something about.
-- Russell (firstname.lastname@example.org), October 30, 2001.