Cleaning of slow shutters

[xkaes]

A quote from Carol Flutot's website at: http://www.flutotscamerarepair.com/Tips.htm

Q What's the best way to store a shutter?

A Keep it in a dry area (off the floor if it's cement, like in a garage). Best to set the speed dial on "T" or "B" and uncocked so there is no tension on the springs. To keep the shutter in shape, you should take it out and exercise it at least once a month, running through once at each speed, and at least 10 times at the lower speeds, to get that slow gear governor moving. Even if you're too busy or have too many shutters... get them out once in a while throughout the year and exercise them or they'll become sluggish over time.

Just because it's plausible, doesn't make it factual. What real-world evidence is there? This "B/T" notion sounds like yet another photographic myth, up there with the idea that higher silver content in papers produces blacker blacks.

[Pere Casals]

It's tension over long periods of time that does the damage.

Or not... it depends on if the spring is poor engineered for the job, or if design is safe to not suffer a "permanent set" if spring elongated at the working distance for long times.

Steel choice for the spring is also important, the right amounts of Mo, Cr, Va, and Si is what makes an alloy resistant to "permanent set", this is beyond the Heat Treating that has to build the Martensite crystals in the material. Also Scragging may ensure the spring takes a definitive ex-factory set.

A "modern" manufacturer of quality springs can guarantee absence of problems, another thing is what a shutter manufacturer was using by 1940.

So for sure that the safe storage is with springs relaxed, but in any case this is because there may be shutters around with poorly engineered springs.

To speak about a known example, the Nikon F90 (or F4, F5, F6, F80, F65... and D1 to D5) shutter is always cocked, as it is always cocked again inmediately after a shot. The F5 and F6 (and digitals, I guess) learn to adjust automatically the rear curtain release from self measured errors, but this feature is not in the F4 for example, and you won't notice an speed change after 20 years in the F4. Simply Copal (the Nikon's shutter manufacturer) used the right steel and coil design.

Did Copal make mistakes in recent LF shutters ? I don't know...

[Leigh]

It's tension over long periods of time that does the damage.

Hasselblad shutters are ALWAYS stored cocked.
In fact, it's impossible to remove the lens from the camera if the shutter is not cocked.

I'm sure you can find plenty of low-quality/cheap springs that will degrade over time.
Springs that are properly designed and manufactured will not.

The common photo myth about cocking/not cocking a shutter is based on a mis-understanding of how spring-driven systems work. A spring in a product is ALWAYS under tension. It will not work if it's relaxed at one end of its operation. That's because the force applied to the mechanism varies with the tension on the spring, decreasing as the tension decreases. Since photo shutters expect uniform force throughout the cycle, the spring must always be tensioned by several turns or it won't work.

Cocked v. un-cocked is simply a difference in the amount of tension on the spring, not its presence or absence.

- Leigh

[LabRat]

The bigger problem is that metals inside shutters oxidize, and over time parts become slightly "sticky" (tacky) or slightly rough (from corrosion) as one part slides or pivots over another and creates resistance slowing up operation, or in worst case, freeze or jam up, and when the mechanism is "forced" past that resistance, damage can happen when parts get bent, distorted, or break...

Most shutters have minimal lubrication, and depend on smooth metal to metal contact, and lube is also for preventing oxidation on those surfaces, but lubes will change viscosity over time, and change the operating parameters depending on hot/cold or age of lubes... Lubes can migrate if the shutter gets really hot and end up in other places where it can gum up other fine moving parts, or become tacky/sticky if they dry up from cold or age...

Exercising a shutter before use is an attempt to move the moving parts and push aside the built-up sticky oxides so everything inside moves with the least resistance...

The C in CLA means to remove old sticky lubes and oxidation so parts don't bind...

Graphite "lubes" are really a very, very fine abrasive that will polish slides/bearings and push oxidation aside if not excessive (where they would need to be cleaned/flushed away for proper operation) and can create a very little space between moving parts so they don't slightly stick together...

There is no one operation for shutters... Each design uses different combinations of differing materials (that interact differently), have lived in differing environments, age, wear, and usage style etc...

Each shutter CLA is basically based on a case by case evaluation basis, few overall "rules" apply and one must apply what the shutter "needs"...

Happy Holidays to everyone, wishing the best and all good things in the coming year!!!!

Steve K

[Pere Casals]

Hasselblad shutters are ALWAYS stored cocked.
In fact, it's impossible to remove the lens from the camera if the shutter is not cocked.

I'm sure you can find plenty of low-quality/cheap springs that will degrade over time.
Springs that are properly designed and manufactured will not.

The common photo myth about cocking/not cocking a shutter is based on a mis-understanding of how spring-driven systems work. A spring in a product is ALWAYS under tension. It will not work if it's relaxed at one end of its operation. That's because the force applied to the mechanism varies with the tension on the spring, decreasing as the tension decreases. Since photo shutters expect uniform force throughout the cycle, the spring must always be tensioned by several turns or it won't work.

Cocked v. un-cocked is simply a difference in the amount of tension on the spring, not its presence or absence.

- Leigh

Yes Leigh, but if the spring alloy lacks Cr, Mo, Va it can happen that a higher constant tension provocates a way higher permanent set. Even a hard steel can build a permanent set if alloy is not right. Problems happen if steel works near of elastic limit and a alloy lacks special metals.

With the Hassy you can release the lens shutter by pressing a pin, to store it with the shutter not cocked for the long term, then it can be cocked again before mounting the lens https://www.youtube.com/watch?v=lE20W-9Q-KQ

With the RB67 (that I use) this can be done (cocking lens before mounting) without tools.

It would be interesting to know if somebody knows about shutters that had been stored cocked long time and had problems with the springs... and in what models that happened...

[Pere Casals]

Happy Holidays !

[Jac@stafford.net]

Graphite "lubes" are really a very, very fine abrasive that will polish slides/bearings and push oxidation aside if not excessive (where they would need to be cleaned/flushed away for proper operation) and can create a very little space between moving parts so they don't slightly stick together..

Just my two-bits worth - graphite lubes are death to lenses. Sure, the shutter mechanism might glide along happily but graphite is almost as insidious as nano tech. It will make its way to lens surfaces even through multiple surfaces. Avoid graphite entirely.

[LabRat]

Just my two-bits worth - graphite lubes are death to lenses. Sure, the shutter mechanism might glide along happily but graphite is almost as insidious as nano tech. It will make its way to lens surfaces even through multiple surfaces. Avoid graphite entirely.

When flooding/blasting the inside of a shutter and is allowed to migrate everywhere... And is very conductive so sync contacts can be easily shorted, and very hard to clean up again...

But graphite can be used on an applicator to burnish sliding/pivoting parts to polish the parts in a controlled way, but should not be a sandstorm cloud inside your shutter...

Happy Holidays, Jac!!!

Steve K

[Drew Bedo]

I have all my shutters CLA-ed by Mike Hakeem at Professional Camera Repair in Houston

https://www.yelp.com/biz/professiona...repair-houston

[xkaes]

Just to confuse things even more, there is a SINAR SHUTTER discussion at:

http://www.largeformatphotography.in...n-Field-Camera

One respondent states:

>>> Just passing on two things that were passed on to me:

Store the shutter on "8 seconds" and not "B".

Also shooting rapidly with the shutter was the most common reason of the shutter breaking.

Both came from a Sinar repair person. <<<

I'll stuck with my "UNCOCKED, AT ANY SPEED" philosophy -- with all due respect to Ralph Nader.