Safe to leave shutter cocked?

[RFFan]

A while ago I came across a warning on the ‘net that old manual rangefinders should NEVER be left with the shutter cocked for any length of time as this will cause the spring to lose tension and hence shutter speeds to become unreliable.

Since reading this I always make sure that I only use the film wind-on immediately before taking a photo hence ensuring that the spring is only under tension for a minimal period of time.

My question is: is this advice correct or just a popular myth? Also, does this ‘warning’ also apply to high-end equipment (e.g. Leica) or only to ‘lower-cost’ mechanical RFs (e.g. Canonets, Hi-matics etc? Finally, is there a 'safe' period of time for which the shutter can be left cocked e.g. between shots within a day but, say, NOT overnight?

 

[Heath]

I have heard this said about the FSU cameras (not only the RFers but also the Zenit's, which share the shutter design). I also keep the camera un-cocked until I am about to take the photo. On my MF cameras, you have to manually cock the shutter with a little lever on the side of it, so I guess I am used to doing it.

Heath

 

[oftheherd]

I don't really know. However, that used to be the advice in all the photo mags and books too. Might be partly because most amatures went days at best, normally months without using their cameras between shots.

I did also read once somewhere on the 'net, someone who claimed to know something about metalurgy, that it wasn't so, that metal tended to hold its tension. Didn't sound right from experience, although most metal seems to hold it at least a while, especially when excercised regularly.

I have always been careful not to leave shutters cocked myself, as I fear it would cause problems. I would rather give up a frame than cause shutter problems.

 

[pvdhaar]

I'm not really a metallurgy expert, but when a spring is made of high quality metal, then it will hold it's tension. It's the number of times it's stressed and unstressed rather than the duration that causes wear. The older the shutter, the more cycles it has probably gone through. But there's more..

That said, with old shutters several other things could also be going on; for starters, the metal can be of poor quality (poor choices of materials and poor hardening leading to susceptibility to deformation). Also, the shutter can be badly designed, stressing the springs near or just beyond their elastic capability.

Especially when a nearly overstressed spring goes through a temperature cycle (like sit in a car on a hot day), then the deformation becomes plastic (as in non-elastic).

You can even test this at home with a paperclip and a couple of matches (don't burn your fingers!). Find the point where the paper clip will just still come back to it's original shape. Now keep it stressed at just that point, and heat it a while with a match where the torsion is highest. You'll see it won't entirely come back anymore..

Conclusion: if you have your gear in a hot car, then untension the springs, otherwise, if you store your gear in a constant temperature environment, then keep the number of cycles to a minimum.

 

[furcafe]

I think that adage is mainly true w/regard to cameras w/leaf shutters (e.g., 120 folders w/Compur shutters), which tend to be more delicate & "watch-like." With a properly-CLAed Leica, Contax, Nikon or Canon RF, etc., I think you would have to let the camera sit w/the shutter wound a long, long time between shots (& why would you let that happen?) for there to be any significant effect on the shutter mechanism.

FWIW, here's a similar discussion w/regard to Canon RFs (including my link to Nemeth's Leica FAQ):

http://rangefinderforum.com/forums/showthread.php?t=10439

 

[wyk_penguin]

If you are the lucky owner of a Rollei35, then your shutter will be cocked a lot.

 

[KoNickon]

...or a Hasselblad. Bad Things happen if you try to remove the lens or back when the shutter (in-lens Synchro Compur) is not cocked, so people leave them cocked. But somehow you don't hear about those shutters wearing out.

That said, I prefer to leave camera shutters untensioned unless I'm in the middle of taking a string of pictures.

 

[jaemyung_shim]

Below is a "copy and paste" from one of the links someone provided:


Store shutter cocked or uncocked?Okay - now are you wondering if it is better to leave the shutter cocked or uncocked when storing the camera for long periods. After all, if you leave the thing wound, won't the springs detension over time? Well no. All mechanical Leicas are designed such that their shutter springs are always under tension. When wound, they are at 75% tension, when uncocked, they relax to 50% tension. Since the shutter springs never get to zero tension, it makes no difference either way.

Here is Sal DiMarco Jnr (Jan 2003) take on this:

When I attended the Leica School in 1971, this question was asked, and I remember the answer very clearly. John Brooks, the instructor said it didn't really matter. The spring tension on a cocked M camera is 75%, and on an uncocked camera, it's 50%. It was a personal choice. Now, today with battey drain being a factor, I would think, uncocked and if you remember it, on the M6TTL & M7 switch the camera to "off" […]