Build a shutter tester for Focal Plane shutters - Cheap, Easy & it Works

[Chan Tran]

Some of the cameras the shutter won't work unless the back is closed. What is the best way to keep that little switch depressed?

 

[Xylo]

My interpretation is that the second curtain takes a lot more time to get to speed. That's why the travel time differs and the overall shutter speed gets faster as the measurement point is shifted to the left of the film gate.

The thing is that the first shutter has gained quite a bit of speed by the time the second shutter starts moving, especially at the lower speeds that are above the flash sync.
Knowing the exact trap position and how long it takes to get there, you can calculate the speed, but in reality that isn't necessary.

When adjusting the shutters, you adjust them so that they just close enough to block the light. Then you adjust either a trim pot or a different spring (often a clockspring) in order to get them to open at the proper speed. But that depends from model to model (I really suck at fixing SLR's )

When I adjust a camera, I just try and get it in the ballpark. Since I never use slide film, I can get away with some pretty sloppy adjustments. I don't mind if it's not perfect, as long as the shutter doesn't stutter while on the move or is too sluggish to give somewhat even results.

 

[Xylo]

Some of the cameras the shutter won't work unless the back is closed. What is the best way to keep that little switch depressed?

I'm still trying to find a solution for my Nikon F-801...
Popsicle stick maybe? I really don't know, but I'm sure the manufacturers had a special tool for that.

 

[Chan Tran]

I'm still trying to find a solution for my Nikon F-801...
Popsicle stick maybe? I really don't know, but I'm sure the manufacturers had a special tool for that.

The manufacturer has the back with the sensor mounted on it. We can do the same but we have to get a back and mount the sensor on it.

 

[alinCiortea]

When I adjust a camera, I just try and get it in the ballpark. Since I never use slide film, I can get away with some pretty sloppy adjustments. I don't mind if it's not perfect, as long as the shutter doesn't stutter while on the move or is too sluggish to give somewhat even results.

You're right. I've shot for a decade not knowing and not caring how accurate my speeds were and I was just fine (and they weren't accurate). But it's a bit frustrating knowing I've done all there was to reabilitate a camera and it's still not up to specs. I know they are old and tired but in my head I started with too high expectations probably.

 

[Niglyn]

PS: shouldn't the LCD light up, even I'd reading nothing, if only VCC and GND are connected? (there's no brightness pot on mine)

Hi,
Good to see your shutter tester is up and running )
The reason your LCD does not work, is that you have an oled display, not LCD.
You need the 2004 LCD with built in I2C module.

I built the device, for much the same reason as you, repairing old cameras & needing a way to correctly align the shutter mechanism.

I have not got my hands on a Zorki yet, too expensive. I have repaired a number of Zenits, which have an almost identical shutter mech.
First thing is to read the service manual. There is one for the Zenit E on the interweb, if you search for it or go to the Facebook group 'Zenit Camera Club' & look in the files section. It describes how the mirror assist spring should be given 2 1/2 turns as a start point & curtain spring 1 needing far more tension than 2.

It then is a case of tweaking. I made two tools so I could easily hold the spring tension on the roller whilst releasing the locking nut. (curtain rollers & mirror assist spring are different sizes) Otherwise, trying to hold the roller with a screwdriver, whilst unlocking the locking nut and holding the camera is a nightmare.

The manual explains to set the camera up at one speed (1/500 I think, but don't quote me) and then the rest will 'be within acceptable tolerance'


These cameras were never that accurate to start with, so do not expect results one would get with a clockwork or electronic shutter.
The closer the two shutter curtain travel times are, the more even the exposure.

Shutter Speed Tolerances

 

[Niglyn]

Wow! That's more than I bargained for...

First thing first... Camera repairing is a new hobby I discovered 5 months ago. So I'm still learning the ropes. For the time being I'm proud to say that I overhauled a Topcon Uni (the one with the Seikosha leaf shutter), a FED2 (it was a can of bits, pieces and screws) and two Zorki 4 (the complete process is here:



though I don't know who in the right mind would actually watch a 2h long timelapse).

I've stripped them down to the last screw, cleaned, polished and lubricated all moving parts but in the end I got stuck at adjusting the curtains (without a proper shutter tester). What I did was film in slow motion the shutter at a reasonable fast shutter speed (usually 1/125) with my phone (records 10 seconds long slow-motions at 960fps so plenty fast for eyeballing it), with a strong light behind and a piece of unexposed film stuck to the film gate. On the piece of film I drew vertical equidistant lines, so I could better assess the rate of travel. Then, when both curtains seemed to have the same speed, tested the speeds on my single LED tester and further adjust the tension. Then go back to the slow-motion and recheck the speeds. And so on.
Moreover, I tested both Zorkis with film and the frames came out evenly exposed.

These are the results on the dual laser tester... I left only the relevant info (IMHO). The difference in curtain speeds makes no sense to me. Maybe I could actually miss it on the film test due to exposure latitude, scene photographed, angle of light etc, but wouldn't I see it on a slow motion?

The part that contradicts me is that testing my OM1, while top speeds are nowhere near what's on the dial, the curtain speeds are almost identical. All my electronically controlled cameras have vertical traveling shutters so I can't use them for cross-checking.

According to my understanding, the second curtain is too slow, right? So I could increase tension until capping occurs and then back up slightly.

All this effort towards the shutter tester was exactly for this: calibrating shutters after CLA/overhaul as good as I possibly can, given the aged springs and reasonable tolerances of these cameras.

Thank you, everybody, for putting up with my silly questions

hi,
Happy to see 'silly' questions posted here, keeps it alive and may also help other peeps. )

If the curtains are travelling at different speeds, on a slo-mo, one would see the slot narrowing or widening, although probably difficult to see by eye.

Laser 1 refers to the readings taken from the right hand side and curtain 1 timings.
Laser 2 refers to the readings taken from the left hand side and curtain 2 timings, as viewed from the rear of the camera.

Looking at your notepad average results,
curtain travel is the time taken for the curtain to travel between the two lasers.


shutter speed average,
Laser 1 is 13mS
Laser 2 is 7mS. So the shutter is open longer on the right hand side (near laser 1)


Curtain Travel Time Average
curtain 1 took 23mS to travel 32mm
curtain 2 took 16mS to travel 32mm. So curtain 2 is moving faster.

The single laser tests,
Show exposure decreases from right to left. This is caused by curtain 2 travelling faster than curtain 1.

If your target speed was 1/125s. Curtain 2 needs tension reduced and curtain 1 needs additional tension.

However, as I said in a previous post, it will drive you insane trying to get these cameras anywhere near correct.

 

[koraks]

@Niglyn Kudos for keeping up the work, the frequent updates, help extended to people giving this a try, etc! Really nice

 

[Niglyn]

Don't mind me... in my head I was still interpreting a 3 sensor tester (with the middle sensor reading the compound exposure).
If the tester reads 'laser 1 seen' when the opening curtain begins the travel, it will use 'laser 2 seen' to calculate curtain travel and 'laser 1 blocked' to calculate exposure time. So, for consistency, I assume laser 1, as long as it's positioned on the right side of the film gate (as seen from behind) means opening or first curtain.

Am I correct?

The microcontroller has a built in microsecond counter, which starts at 0 and counts up in microseconds.

As curtain one travels, it will uncover the first laser, so it will be 'seen'
Laser 1 seen >>>>record microsecond counter value1

Curtain one continues, reaching the second laser, where it will uncover the second laser, so it will be 'seen'
Laser 2 seen >>>>record microsecond counter value2


curtain two travels and blocks the first laser
Laser 1 blocked >>>>record microsecond counter value3

Curtain two continues, reaching the second laser, where it will block the second laser,
Laser 2 blocked >>>>record microsecond counter value4


From these four values it is simple maths to calculate exposure & curtain travel time.
Subtract value1 from value 2 and it gives the time curtain one took to travel between the two lasers.
Subtract value3 from value4 and it gives the time curtain one took to travel between the two lasers.

Subtract value1 from value3 to give exposure time as seen by laser 1
Subtract value2 from value4 to give exposure time as seen by laser 2.

 

[Niglyn]

@Niglyn Kudos for keeping up the work, the frequent updates, help extended to people giving this a try, etc! Really nice

Thanks for the vote of confidence )

Next up will be build a cheap exposure meter (that works)

Only uses four parts, including battery & charger. Less than £14 from Aliexpress.

Designed to replace or confirm readings on an old camera's reflective light meter.

All seems to be working ok. Waiting for a battery powered board to arrive.

Don't want to post the code or kitting list until I can check it all works, out in the wild.

 

[koraks]

Next up will be build a cheap exposure meter (that works)

Cool! Prototype looks promising. What are you using for a light sensitive element; an LDR module?

 

[Niglyn]

Cool! Prototype looks promising. What are you using for a light sensitive element; an LDR module?

BH1750 light module, gives reading output directly in Lux, up to 122000. Also can be sw calibrated.

 

[koraks]

Oh, that's very convenient. Should work just fine in most circumstances - probably better so than the kind of meters it's intended to replace!

 

[alinCiortea]

Hi,
Good to see your shutter tester is up and running )
The reason your LCD does not work, is that you have an oled display, not LCD.
You need the 2004 LCD with built in I2C module.

Oh... well my mistake then

Regarding the adjustments of the curtains.. I've done my custom tool as well. It works wonders but unfortunately it only fits zorki 4 locking nuts. For the time being I have gathered a handful of soviet rangefinders as I deemed it a good idea not to learn basic skills on Leica material. Among them two FED 2, one FED 5, one Zorki C, one Zorki 4 and one Zorki 4k. Every one of them has a different style locking nut (except 4 and 4k that are similar). In the Zorki 4 even the two nuts are slightly different. On the other hand I'd rather spend 10 minutes editing the design and then print a couple 'keys' at work than adjusting them without the keys.
If anyone is interested I can upload the STL file. I'll most likely make one for FED 2 as one of the two is DOA and awaiting overhauling.



On both Zorkis I started with 3 turns of tension on first curtain and 1 and 3 quarters on second curtain and adjusted as necessary. I'll redo the adjustments from scratch on one of the bodies after I'm done replacing the curtains on a Nicca 3-S that I have high hopes from

Thank you so much for the in-depth explanation of the logic behind the tester. It makes so much more sense now.

 

[Xylo]

Making custom tools is always one of the best things to do on a 3D printer.
I really need to make one for my Graflex as it would reduce the amount of disassembly required to adjust the Kalart rangefinder.

 

[Niglyn]

I have (almost) run out of ideas for more things to add to the shutter tester, so have started a thread on the exposure meter. It all works fine on the bench, but until the battery arrives, I cannot add the standby, auto-off etc & take it out & about to test.

Build an exposure Meter, Cheap, Easy & it Works

#1 Hi, Following on from my 'Build a Shutter Tester, Cheap Easy & it Works, I thought I would start a thread for my latest project, as the title suggests, to see how much interest there is. The aim is to build an exposure meter for old cameras that either have a failed, or un-trustworthy...

www.photrio.com

For the shutter tester, I'm planning to add connection to the flash PC socket, so flash firing time can be recorded.

Am also thinking about adding a lux / EV sensor. Theory being you can add your own light source, LED, halogen, tungsten, what-ever you choose, controlled with a dimmer. The shutter tester can then show you the EV value. You dim the light till EV15 for example and then check the camera light meter or auto exposure gives you the correct metering, e.g. EV15 = F16 @ 125/s at 100iso).

 

[norbit0]

Hi,

I've noticed that in the version 3.0.1 1st and 2nd curtain speeds are swapped on the LCD:

C2 = shCurtainspeedMilliS1
C1 = shCurtainspeedMilliS2

but in 2.9.9:

C1 = shCurtainspeedMilliS1
C2 = shCurtainspeedMilliS2

or am I missing something?

Best regards

 

[Niglyn]

or am I missing something?

Opps
Yep, thanks, well spotted. Thought curtain two would be better moved to the right side of the LCD, but only did half the job )

 

[alinCiortea]

Hello, people! It's me again with my noob questions...

I'm currently adjusting yet another FED2 and I have the same issue as always: the tester says one curtains runs twice as fast as the other. My eyes says that's not true. My slow motion recording (huawei p30 pro phone, 960fps) tends to agree with me. The speeds are not important right now because I'm trying to find the correct curtain tension first and then adjust the second curtain position for the closest possible speeds (given the age of the springs, the original curtain positions will probably translate in about one stop or more of overexposure). These are the averages for 1/250

AVERAGES LASER2 LASER1
shutter Speed Av mS 10 6 13
Curtain Travel Av mS 10 21 28

Shutter Speed Av Vul 10 1/159 1/76

I can't help but wonder if these values should be interpreted differently depending on type of shutter. What I mean by this is the fact that I tested 6 cameras so far that use the same shutter type (Leica II / III clone or adaptation): 3 FED2, 2 Zorki 4, one Nicca 3S and all of them give similar results, with one curtain being read as twice as fast as the other. 4 of them have been film tested and I didn't notice an overexposure gradient (but I didn't photograph even subjects either)
I've also tested 3 other cameras with different shutter design (Praktica Super TL, Topcon IC-1 and Olympus OM1) and they all read similar CTT for the two curtains.
It's true that I changed the curtains in all six aforementioned cameras but something is weird and I just can't understand it.

If your answer is a definitive 'you're drunk, sit down' and you tell me that the shutter tester can't lie, the readings are not interpretable and the mistake is mine I'll be very happy because knowing the issue will help me fix the issue.

Thanks again!

PS: I've attached a slo-mo video of this shutter at the speed used to read the averages (1/250). Seems decently even to me.

 

[Niglyn]

What trickery did you use to make the slo-mo? surely witch-craft was involved?

You had me worried at first, I thought my code was goofed, but.......

The witch-craft, to my eyes, shows that the second curtain is moving slower than the first,
the slit is far wider towards the left side of the gate, than it is at the right. It also has a nasty curtain bounce.

In your video at 5s, we can see second curtain release. The slit seems to be 1/4 of the frame width, which would be 1/1250s.
Now at 6s, the first curtain appears to speed up, widening the slot.

This is proved by the figures, using your first line 10 6 13

10 samples
6mS for the first curtain to move between the two lasers
13mS for the second curtain to move between the two lasers

The time 6mS and 13mS is not travel speed, i.e more is faster (travelling in a car at 30mph or 40 mph)
but it is time taken for the curtain to travel between the two lasers, so the higher the number, the more time it has taken.

Please keep asking questions, posting your thoughts & results. It keeps the thread alive.

 

[alinCiortea]

yes, there is a difference in speed that I can also see in the video and maybe that's just enough to explain the numbers. I'm still trying to think how the tester thinks.

I've used the laser test code to identify the lasers and laser 1 is at the right of the film gate, laser 2 is at the left. Does that mean that in the results laser 2 represents first curtain and laser 1 represents second curtain? (and that the shutter tester code always puts in the first column of the serial monitor whichever laser is actually responsible for first curtain?)
Because this is also very important. I might have adjusted the wrong curtains the whole time )

The slo-mo trickery is actually a photo function of the camera app. It waits for something to move inside a user selectable square and as soon as it senses movement it generates a 10 seconds video of the movement. I believe it constantly records on a loop and when something moves it only retains a couple seconds before and a couple after the event. Or some chinese voodoo like that

PS: could you please explain why it would be better to have the lasers in front of the camera and the receivers at the back? Mine has the lasers behind the camera so I can make sure they are within the frame.

PS2: as for shutter bounce... yes there's a lot of bouncing but the camera has no brake for the second curtain so it's a design issue. That's one of the reasons I'm trying to keep the tension as low as possible and adjust the speed by modifying the curtain placement. A pig of a job.

 

[alinCiortea]

I tried one more thing. Got the camera in B, depressed the shutter and then, without releasing the shutter button I quickly lifted the camera from the tester. As a result I got 2ms travel time for 'laser 2' and 22ms for 'laser 1', meaning laser 1 is in fact curtain 1. And that's completely mind boggling for me. That means the tester tells me the second curtain travels faster than first curtain while the slo-mo shows the opposite.
Slight tension adjustments most often translate in speed differences within the error margin of the shutter so it's very hard to approach things by trial and error without knowing what's what.

 

[Niglyn]

yes, there is a difference in speed that I can also see in the video and maybe that's just enough to explain the numbers. I'm still trying to think how the tester thinks.

I've used the laser test code to identify the lasers and laser 1 is at the right of the film gate, laser 2 is at the left. Does that mean that in the results laser 2 represents first curtain and laser 1 represents second curtain? (and that the shutter tester code always puts in the first column of the serial monitor whichever laser is actually responsible for first curtain?)
Because this is also very important. I might have adjusted the wrong curtains the whole time )

The slo-mo trickery is actually a photo function of the camera app. It waits for something to move inside a user selectable square and as soon as it senses movement it generates a 10 seconds video of the movement. I believe it constantly records on a loop and when something moves it only retains a couple seconds before and a couple after the event. Or some chinese voodoo like that

PS: could you please explain why it would be better to have the lasers in front of the camera and the receivers at the back? Mine has the lasers behind the camera so I can make sure they are within the frame.

PS2: as for shutter bounce... yes there's a lot of bouncing but the camera has no brake for the second curtain so it's a design issue. That's one of the reasons I'm trying to keep the tension as low as possible and adjust the speed by modifying the curtain placement. A pig of a job.

Hi,
The simple shutter tester, when it was simple, just measured the seen & not seen times of the lasers, as the curtain unblocked and blocked them, This can be seen on the first line of the printout where the raw times are given. This was also for me when developing, so I could check the maths. This gives four microsecond values. From these, everything else is computed.

So,
The microcontroller has an internal clock that runs automatically on start-up. It counts up in micro seconds and never stops.
When laser 1 is unblocked as the first curtain opens, the micro second clock time is recorded (eg 0)
When laser 1 is blocked as the second curtain closes, the micro second clock is recorded (eg 33000)
When laser 2 is unblocked as the first curtains opens, the micro second clock time is recorded (eg 3000)
When laser 2 is blocked as the second curtain closes, the micro second clock is recorded (eg 36000)


Laser 1 blocked - laser 1 seen = exposure as seen by Laser 1
33000 - 0 = 33000 micro seconds. This is 1/30s exposure.

Laser 2 blocked - Laser 1 seen = exposure as seen by Laser 2
36000 - 3000 = 33000 micro seconds. This is 1/30s exposure.


Laser 2 seen - Laser 1 seen = how long it took for curtain 1 to move from the first laser to the second
33000 - 0 = 33000 or 3mS

Laser 2 blocked - Laser 1 blocked = how long it took for curtain 1 to move from the first laser to the second
36000 - 33000 = 33000 or 3mS


The above is for 1/30 shutter speed, when curtain 1 fully opens before curtain 2 starts to close.

At faster speeds curtain 2 could be blocking Laser 1 before curtain 1 has reached Laser 2.
The code does not care, it just takes the first instance of seen and blocked for each Laser, giving four readings.
It will expect laser 1 to be seen first and laser 2 to be blocked last etc. There is not much error checking in the code,
I get it to spit out what ever it sees. So, as you have found, if you move the camera up vertically, strange results will be printed.

Laser 1 is on the right and Laser 2 on the left, as viewed from behind the camera. The displays also print out in the same orientation.

You can turn the camera around and the exposure reading will be correct. This can be a quick proof check if you are getting goofy readings.
Curtain speeds will of course be wrong.

Having the lasers point at the gate makes it easy to align the camera. Even though the lasers are very low power, one should never look directly into a laser, so having them point into the mirror box and aligning via the viewfinder is not a good idea. Also some people do not like the idea of a laser shining onto their exposure meter within the camera. I run my lasers from the 3.3V output, so they are dimmer than if running from 5V. Not sure if the latest schematic shows this.

A point also worth noting is the shutter speeds we know are not actually correct, they are slightly changed to make it easier for the human brain. Nikon in their manuals warn for example, that a display of 30 seconds is actually 32 seconds. This can be proved by timing the exposure.

32s 16s 8s 4s 2s
1s 1/2s 1/4s 1/8s 1/16s
1/32s 1/64s 1/128s
1/256s 1/512s 1/2048s

The shutter tester code uses the nominal values that we all know. I have thought of changing the code to use the exact and correct figures above, but it may confuse people. The screen is cluttered enough with out adding nominal and actual target values.


Not sure what camera you are playing with. A few photos of the shutter mech would be good. Trying to adjust exposure by altering the curtain width may not be a good idea. As flash sync speed (eg 1/30), curtain 1 should be fully open before curtain 2 starts to close.
At 1/60, second curtain starts to close when firsts curtain has travelled half way.
At 1/125, second curtain starts to close when first curtain has travelled a quarter of the way etc.
Also, a wider gap would mean at the end of the travel, the two curtains would not slightly overlap. This is required when resetting the shutter, to ensure it is lightproof when travelling back across the gate.

Please ensure you are using the latest version of the code. a slight bug crept in between version 2.9 and 3, as are noted in the posts above.

 

[Niglyn]

I tried one more thing. Got the camera in B, depressed the shutter and then, without releasing the shutter button I quickly lifted the camera from the tester. As a result I got 2ms travel time for 'laser 2' and 22ms for 'laser 1', meaning laser 1 is in fact curtain 1. And that's completely mind boggling for me. That means the tester tells me the second curtain travels faster than first curtain while the slo-mo shows the opposite.
Slight tension adjustments most often translate in speed differences within the error margin of the shutter so it's very hard to approach things by trial and error without knowing what's what.

Yep, that seems like the correct result you would expect. It is not a result that is correct as this is not how the shutter tester was designed to operate.
There is very little error checking of the results, it just spits out the maths based on the four laser readings.

So,
when you pressed the shutter, Laser 1 seen timer started ticking away.
When the curtain passed laser 2, laser 2 seen timer started ticking away.
So laser 1 will have a higher value (22mS) than laser 2 (2ms) as laser 1 clock starts first.

The correct sequence should be laser 1 gets blocked and then laser 2 gets blocked.
However, by lifting the camera up, you could block both lasers at the same time, which of course can never happen with the shutter curtain,
or you could have blocked laser 2 slightly before laser 1, which again can never happen
or you could have blocked laser 2 slightly after laser 1.

When I'm tinkering with the code, I use a piece of card with a slot cut in it (two slots for shutter bounce testing) rather than a camera, & wave them in front of the Lasers. I can get weird results when moving the cards back, as they are not moving in the correct sequence a focal plane shutter would.

The Arduino is stuffed full of code, so there is little space for anything else, but I might add more error checking & diagnostic help in the ESP32 version. These are tasks for the winter months.

 

[alinCiortea]

Thank you for the in depth explanation once again!

What I'm really interested to know is if Laser 1 în the printed results in fact gives the results for the opening curtain. Meaning am I correct to adjust first curtain based on Laser 1 values or am I having it all wrong?

My lack of understanding derives from the fact that both lasers must be involved for the assessment of each / any curtain.