Adjusting shutter speed on old cameras

[mecedo]

I want to ask people experienced with servicing cameras. I've tested shutter speeds on my 15 old SLR cameras using oscilloscope and circuit with fast phototransistor BPW34 (see results on attachment). The common denominator is that most of the cameras have problem with speed 1/500 and almost every camera has problem with speed 1/1000. I've tried to adjust shutter speeds in one Minolta XG-M, which has two potentiometers for adjusting (one for 1/60s and another for 1/1000s). Adjusting speed for 1/60s is very easy. Little turn on potentiometer and speed is adjusted perfectly. But adjusting 1/1000s is impossible. Turning potentiometer has a little impact on speed. Even at the end of the potentiometer range speed is far from ideal.
So, is it possible that shutter rails should be lubricated first on every camera? Or maybe shutter springs become weak after 20-30 years?

 

[johnf04]

Is there a problem when you take photographs with these cameras?

 

[tunalegs]

I want to ask people experienced with servicing cameras. I've tested shutter speeds on my 15 old SLR cameras using oscilloscope and circuit with fast phototransistor BPW34 (see results on attachment). The common denominator is that most of the cameras have problem with speed 1/500 and almost every camera has problem with speed 1/1000. I've tried to adjust shutter speeds in one Minolta XG-M, which has two potentiometers for adjusting (one for 1/60s and another for 1/1000s). Adjusting speed for 1/60s is very easy. Little turn on potentiometer and speed is adjusted perfectly. But adjusting 1/1000s is impossible. Turning potentiometer has a little impact on speed. Even at the end of the potentiometer range speed is far from ideal.

So, is it possible that shutter rails should be lubricated first on every camera? Or maybe shutter springs become weak after 20-30 years?

Shutter speeds shouldn't really be adjusted until everything else has been sorted out. Does it need a cleaning? Lubrication? That should happen first. Until everything is clean and smoothly operating, shutter speeds can be erratic. Once that's taken care of, even if they're off, at least they'll be consistently off and one can attempt to adjust them. Even so, don't get hung up if you can't bring them in to better than a half stop worth of accuracy, it is an old camera (and probably weren't any more accurate than that when new).

 

[mecedo]

Does it need a cleaning? Lubrication? That should happen first.new).

Hard to say. I don't know how to decide. Is it possible to decide by looking to shutter rails?
In service manuals there's no information about cleaning and lubricating shutter mechanism.

and probably weren't any more accurate than that when

I think they were better (but not ideal, of course) when they were new. As you can see Minolta X-300 which is the newest from this group has the lowest deviation

 

[Sarcophilus Harrisii]

The pots are def for two speeds? Not one for each curtain? I've adjusted the shutter of older mechanical Minoltas but have no experience working on later types which are of less interest to me hence, my question. As has been said, is it actually problematic for your results?

 

[Dwig]

Before you can adjust the exposure times ("shutter speeds") you have to first adjust the curtain travel times. If the curtains are not traveling at the correct speeds you'll never be able to get the correct exposure times by adjusting the controls (electronic or mechanical) for the time delay between curtains. You can get close at lower exposure times, but at the faster speeds you'll never get close.

Professional testers generally used 3 sensors, one at each end of the image and one in the center. They would report the time it took each curtain to travel across the opening and the duration at each of the three spots. With that information, and the manufacturers specs for the shutter, you can adjust the tension springs on the curtains to get the travel times correct and to balance the left-center-right exposure times so that they are uniform.

 

[flavio81]

I want to ask people experienced with servicing cameras. I've tested shutter speeds on my 15 old SLR cameras using oscilloscope and circuit with fast phototransistor BPW34 (see results on attachment). The common denominator is that most of the cameras have problem with speed 1/500 and almost every camera has problem with speed 1/1000. I've tried to adjust shutter speeds in one Minolta XG-M, which has two potentiometers for adjusting (one for 1/60s and another for 1/1000s). Adjusting speed for 1/60s is very easy. Little turn on potentiometer and speed is adjusted perfectly. But adjusting 1/1000s is impossible. Turning potentiometer has a little impact on speed. Even at the end of the potentiometer range speed is far from ideal.
So, is it possible that shutter rails should be lubricated first on every camera? Or maybe shutter springs become weak after 20-30 years?

I don't think you can reliably test speeds faster than 1/30 with only one (1) phototransistor. On the other hand your test setup is perfect for testing the slow speeds.

On a focal plane shutter, speeds that are above flash-sync-speed (X-speed) up to the top speed are regulated by narrowing the slit opening. Electronic testers for such speed have more than one phototransistor, to be able to test correctly the result. Because you would need to know the curtain travel time AND the opening time.

Also, you need to make sure the slit stays uniform through the travel.

All this criteria is more easily tested using a CRT television, this is explained elsewhere on the net (using a TV as a shutter tester). This is good for the fast speeds AND also allows you to check if the slit opening stays constant !!

As for adjusting the actual fast speeds, as explained above you first need to make sure that the camera is lubricated perfectly. If the camera is perfectly clean and lubricated, chances are that speeds will automatically 'correct' itself. Actual adjustment is performed by varying the slit opening (depends on the camera maker) and/or adjusting the curtain tension -- which I attempted once and is a headache. But then, i don't have a shutter tester.

Otherwise perhaps you can use an Arduino microcontroller and three or four phototransistors and build a fully featured shutter tester!!
Another possibility would be to photograph the actual exposure through the image plane using a DSLR camera. This would tell you if the actual light coming through is OK and will show you any exposure evenness problem!!

 

[johnf04]

Remember, too, that the Pentax ME Super, the Cosina, the Revue, and the Praktica, have vertically running metal bladed shutters, quite unlike the roller type shutters on other cameras.

 

[mecedo]

Currently I'm using digital camera but I want to back to analog photography too. Collecting old SLRs became my hobby in last time. I want to clean and adjust them as well as I could. After that I'll start to taking photos.

Before you can adjust the exposure times ("shutter speeds") you have to first adjust the curtain travel times

Ok. I'll build additional circuit http://www.kyphoto.com/classics/combinationtester.html for measuring curtain travel times and adjusting tension springs on the curtains.

"I don't think you can reliably test speeds faster than 1/30 with only one (1) phototransistor"

Also worry about it but I think it's not so bad. I've attached 2cm black pad with narrow hole (3mm diameter) at the front of phototransistor to narrow field of view. Graphs from oscilloscope are very clear and well shaped. But I'll build additional circuit with two phototransistors as mentioned above.

As for adjusting the actual fast speeds, as explained above you first need to make sure that the camera is lubricated perfectly.

What kind of lubricator do I have to use for shutter rails? Silicone spray?
Or maybe it shouldn't be lubricated because lubricator only harms? Maybe only cleaning is enough?

 

[Sarcophilus Harrisii]

I'm not quite sure what you mean by the "rails" sorry. But I'd generally avoid using silicone within a camera or other optical device. It's difficult to remove it from surfaces it contacts and has the potential to be very problematic in certain locations. I am used to working on older fully mechanical cameras, generally lighter fluid would be a safe choice with those, with a more modern camera using electronics you may be better off with electrical contact cleaner. But it's important to have a clear understanding of what you're trying to achieve with any cleaning process, which components you're cleaning, and why. Not knowing much about the later Minoltas I can't be much more specific than that, sorry, but I'd obtain further information about the specifics of the design before proceeding with further dismantling, using cleaning fluids or lubricating anything.

If the shutter relies on electrical power to function it is always worth considering the implications of any faults in the power circuit. The affect of these may vary from type to type but in some cases a continuity fault or excessive resistance may potentially affect the accuracy of the unit if it relies on certain voltages to run properly. If you haven't confirmed this as being in good condition it's probably not a bad idea to check it out.
Cheers
Brett

 

[mecedo]

I'm not quite sure what you mean by the "rails" sorry

I mean guides (top and bottom on roller shutter) on which curtains travels from one side to another.

 

[sevo]

Remember, too, that the Pentax ME Super, the Cosina, the Revue, and the Praktica, have vertically running metal bladed shutters, quite unlike the roller type shutters on other cameras.

A.k.a. Copal Square (and its Pentacon counterpart). These were far more common than that, standard on just about every new SLR generation designed from scratch after the mid sixties, apart from Canon and Olympus (which stuck to cloth shutters for one more generation).

 

[Pherdinand]

One sensor is sufficient, but you do need to place it to at least two locations and run the test twice. Also make sure the difference you see is reproducible, not just measurement error or shuot to shot variation.
For a sideways travelng shutter curtain, several measurements with the sensor in the left corner and several at right corner will give you all the info you need.
If the two averaged sets show same value but deviating from expected, you get the table as you show.
If they show a different value for different positions of the sensor, your curtans travel not with the same speeds. Which one goes faster and which ne slower, you can figure out from the logic of travel direction and measured shutter open time difference.

AFAIK the electronics indeed control the "open time" and not the individual shutter curtain speeds. At least for some of the cameras this is the case. They control the delay of the 2nd curtain. How fast they actually move is in these manual-cocking cameras controlled by spring tension.

 

[mecedo]

AFAIK the electronics indeed control the "open time" and not the individual shutter curtain speeds. At least for some of the cameras this is the case. They control the delay of the 2nd curtain. How fast they actually move is in these manual-cocking cameras controlled by spring tension.

In Minolta X-700 Service manual is chapter for adjusting curtain's speed - sprockets and ratchets.

 

[sevo]

In Minolta X-700 Service manual is chapter for adjusting curtain's speed - sprockets and ratchets.

In every service manual there will be a chapter on speed adjustment, as the core speed governs all speeds and shutter fading. But every small format focal plane shutter I am aware of has only one speed (essentially the speed declared as x-sync speed), all times are created by slit width adjustment (speeds shorter than x) respectively second curtain delay (speeds longer than X). Only large format and early medium format SLRs tend to have user accessible shutter tension knobs - and correspondingly a tension*slit width table rather than shutter speeds directly printed on one knob).

 

[nobbylon]

I built a couple of testers a few years ago. They seemed accurate up to about 1/1000 sec.
As others have said, service the camera first and more than likely the speeds will return to normal.
I've never had to adjust slit width on any Leica I've had. One of 2 things is usually an issue.
!/ slow first curtain resulting in perceived high speed or none existant 1/1000th
2/ slow second curtain causing none closing shutter.
both caused by sticky old lube and grime and not spring tension however if someone has been in there and had a twiddle with the 2nd curtain tension both scenarios could result.
If tensioned too high the camera feels to me highly strung, edgy etc.
I first lube the camera and then check the speeds using a crt. The pattern will tell you whats going on. On Leica M that I've done and Nikon F, F2 F3 and probably most fp shutters the closing curtain speed has always been fractionally less than opening curtain speed evidenced by the increasing gap on the sloping pattern toward the bottom of the frame.
If lubed properly and not giving the correct pattern then curtain speed can be adjusted. If after this the speeds are still off then slit width could be adjusted.
Ater all this adjust the curtain brake.
This has been my method for the last 10 years and works fine with accurate and even exposure accross the frame.