Tempor shutter spring

SalveSlog · Jul 18, 2014

My cleaned Tempor shutter runs fine at speeds from 1sec to 1/100sec. But the 1/250 is only about one half stop faster than 1/100. The cause of this may be that I did not clean it well enough, but I suspect that the real cause is that the spring may have lost some tension.

Would it be possible to shorten the spring to get more tension, or is this just a silly idea from this newbie?

bernard_L · Jul 18, 2014

silly idea from this newbie

Yes. Too much risk for an uncertain benefit. It is common that the highest shutter speed is slow.

My cleaned Tempor shutter runs fine at speeds from 1sec to 1/100sec

That is good news. Be happy and use it. Have good pictures.

baachitraka · Jul 18, 2014

Don't do it. Truth is you may never reach 1/250 even when it was new. ;-)

David Lyga · Jul 18, 2014

Even a bit of oil or debris will compromise the swiftness of this extremely fast speed (for this type of shutter). And, being under tension for years and years does not help. (Indeed, I wonder how much slower it would be if cold?)

Theoretically, I would flush it out with lighter fluid (after removing all lens elements) and then let it dry thoroughly. That might help greatly, but there is always the problem of getting lighter fluid into the helicoid and transferring that gunk onto those shutter blades. Thus, maybe that 'advice' should rest within the realm of theory if you do not know what you are doing. However, if you can remove the shutter from the helicoid and clean the threads COMPLETELY, you are free then to flush the mechanism thoroughly with lighter fluid. That is what I would do. Actually, the spring looks pretty robust to me and does not seem to have suffered from 'years of being under tension'.

If not, perhaps, in your immediate case, the best thing to do is to deal with it as it is. 1/100 is not too slow and will stop at least some action. But, beware, if cold: does it fire as rapidly? Make tests. - David Lyga

AgX · Jul 18, 2014

David Lyga said:
I wonder how much slower it would be if cold?)

With sinking temperature the spring-constant rises, a spring becoming more forceful, shutter time becoming shorter.

But other factors as for instance rising oil viscosity (in case of lubricated shutter) are of effect too.

BrianShaw · Jul 18, 2014

baachitraka said:
Don't do it. Truth is you may never reach 1/250 even when it was new. ;-)

x2

David Lyga · Jul 18, 2014

That is very interesting, AgX, and I had not thought of the spring becoming STRONGER with lower temperatures. However, in the real world, (and as you rightly infer) the viscosity factor would probably more than counteract such force. Thus, in the cold, the shutter could still operate more slowly despite a somewhat stronger spring tension.

And BrianShaw's reiteration of baachitraka's warning is also relevant: Even when new these high speeds on such rather crude shutter mechanisms were probably more for marketing and visual convenience than for dead accuracy. As I originally said, 250 is a VERY high speed for such a shutter and such high speeds are the first to go as such shutters age (thus, the caveat not to store such cameras at the higher speeds). Also realize that on leaf shutters there is a time lag where the leaves are only partially open (adding even to depth of field, perhaps) - David Lyga

shutterfinger · Jul 18, 2014

That spring you picture the end of looks like the main cocking spring. Speeds faster than 1/100-1/125 use a booster spring.
How are you testing the speed?
Photodiode type testers with the sensor at the center of the shutter rarely read the faster speeds accurate.

Test the shutter with some real life exposures using equivalent exposure of the same scene, process all in the same batch, then read the densities of the negatives. Scanning at default manual settings and comparing the unedited results in image editing can show you the density differences also. Testing 1/2 stop slow will most likely shoot within 1/3 stop density difference from the other speeds. I use ISO400 film to test as slight differences in exposures show up where they would be masked on slower film.

The only thing I would put lighter fluid on is something I'm preparing to burn, matches at the ready.

David Lyga · Jul 18, 2014

Yes, test, but first test that aperture: test a proven lens with aperture at, say, f8 for one full second. Then test this camera's lens at f8 for, also, one second. If the two negative densities are the same, proceed with the (much faster) shutter-timing test. - David Lyga

SalveSlog · Jul 19, 2014

Thanks to all for answers! So I won't mess with the spring.

Shutterfinger,
yes I test with a diode that records change in light intensity. I wrote about my testing of the same shutter (there was a url link here which no longer exists).

E. von Hoegh · Jul 19, 2014

AgX said:
With sinking temperature the spring-constant rises, a spring becoming more forceful, shutter time becoming shorter.

But other factors as for instance rising oil viscosity (in case of lubricated shutter) are of effect too.

This is correct, watchmakers knew this 275 (or more) years ago.
Shortening the spring will increase it's rate and the tension it is under, but actually make it able to store less energy. I'm not familiar with the Tempor, but if the blades are made of steel demagnetizing it may speed it up a bit. I've gotten a full stop by doing this.

SalveSlog · Jul 19, 2014

Demagnetizing sounds interesting, but is there reason to believe that they are magnetized?! (In other words: will any steel be more or less magnetized?)

AgX · Jul 20, 2014

I admit I never thought of shutter blades being magnetized.

But... I also hardly see a way those blades could have become magnetized by accident and no way by use.

DWThomas · Jul 20, 2014

AgX said:
I admit I never thought of shutter blades being magnetized.

But... I also hardly see a way those blades could have become magnetized by accident and no way by use.

I have a vague recollection from many years ago reading that you could lay a steel rod in a north-south direction and hitting it with a hammer would leave it magnetized. I suppose the theory is that random magnetic couples would be realigned to a linear orientation. As such, perhaps the clicking and clanking of a shutter could magnetize a blade or three. (Ah, a PhD research project! )

AgX · Jul 20, 2014

Yes I know, but the stress should not be sufficient to magnetize the mounted shutter blades anything but a tiny spot if there would be stop to hit.
If not laying the blades flat and hammering them.

E. von Hoegh · Jul 21, 2014

DWThomas said:
I have a vague recollection from many years ago reading that you could lay a steel rod in a north-south direction and hitting it with a hammer would leave it magnetized. I suppose the theory is that random magnetic couples would be realigned to a linear orientation. As such, perhaps the clicking and clanking of a shutter could magnetize a blade or three. (Ah, a PhD research project! )

That's correct, also tapping a bit of magnetized steel can weaken it's magnetism.
As for how the things got magnetized, I never found out. But you might be surprised what a strong field can exist on top of for instance a bookshelf stereo speaker - if you don't believe me wave a gaussmeter over one sometime.
Watches with steel/brass bimetallic balances and steel balance springs pick up magnetism often enough, why not shutters?

E. von Hoegh · Jul 22, 2014

SalveSlog said:
Demagnetizing sounds interesting, but is there reason to believe that they are magnetized?! (In other words: will any steel be more or less magnetized?)

I routinely degauss every watch I work on, you'd be surprised how many have some trace of magnetism.
Also - I use railroad watches as my day in-day-out watch, switching watches every few months so they all get run regularly. Whenever one inexplicably alters it's rate, the first thing I do is stick it in the degausser. That almost always returns the watch to it's normal performance, if it doesn't the watch has either gotten dust in it or needs to be cleaned due to aged lubrication.
Back in ye goode olde days, when I set the convergence on a color TV it was wise to orient the CRT so the screen was facing due magnetic north or south - so the field cut the shadow mask at the screen at right angles.
So the earth's field definitely has an effect.

Tempor shutter spring

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