Testing leaf shutter consistency across speeds

[miha]

I'm testing three leaf shutters: two MamiyaSekor lenses with Seiko Shutters and one Schneider lens in a Compur shutter to check exposure consistency across shutter speeds. I'm not trying to confirm if 1/500 is truly 1/500 etc, but rather if it behaves as one stop faster than 1/250, which should be one stop faster than 1/125, and so on. I’ll shoot a uniformly lit white wall and compare exposures, e.g., 1/500 at f/4 should match 1/250 at f/5,6 if the speeds are evenly spaced. For the Mamiya lenses, I’ll use one roll of 120, testing six speeds per lens from 1/500 to 1/15 (I don't need to go lower since I usae the camera mostly hand-held). For the Schneider lens, I’ll use a second roll in a roll-film back, testing down to 1 second (10 shots available). Both rolls will be developed together. Does this approach seem sound, or am I missing something?

 

[koraks]

I'd honestly just use some kind of shutter testing setup instead of film. Apart from the cost involved of shooting film for this purpose and the amount of work/time needed, there's issues like development variations etc. that may spoil the broth.

The simplest 'shutter tester' is to make an audio recording of the shutter and then use a tool like Audacity to determine the time between opening and closing. This has worked well for me on leaf shutters as they produce a clearly identifiable, audible sound on both ends of the cycle. The fastest speeds may be more tricky to record (although I've had decent success even with these). I used a smartphone for this, but a microphone input on a computer/laptop etc. might also be used. In a similar vein, you could use the high-speed video recording mode on a smartphone and then count the number of frames that show the shutter being open. However, it takes a high framerate to get accuracy on the higher shutter speeds, so the sound recording approach generally works better (and involves less data).

More fancy approaches would involve one or more optical sensors and a light/laser beam positioned in e.g. two places (center of the shutter and somewhere along the edge), with a microcontroller recording the time period between the open and close events. There are DIY options as well as commercial (second hand) solutions.

 

[miha]

Thanks for the suggestions! I can see how the audio or video methods could be more efficient, but I’m more of a visual person, and I like seeing the actual results on film since that’s how I use the gear. I’ve never used audio tools like Audacity, so there’d be a bit of a learning curve for me. A proper shutter tester would be ideal but the local repair shop I used to go to closed down years ago, so this film test is the most practical option for now. I also don't see any issues with development variotions since both films would be developed together in thr same tank.

 

[koraks]

Two rolls will not be sufficient to determine consistency of shutter speeds at various speeds across two lenses. 20 rolls of film would be a more realistic plan.

I understand what you say, but the kind of testing you're setting up for isn't very conclusive to say the least. If you want to put two rolls into this, I'd suggest just shooting random subjects and evaluate the results; if the exposures look OK then don't try to fix any problem. If there are inconsistencies, do proper testing to avoid getting dragged into some wild goose chase with too many variables.

 

[acrobatic_citron]

This assumes all the shutter speeds are correct in the first place or rather if they move they move together which in the handful of lenses ive tested is not the case ( 1/8 can be way out but 1/15 and 30 are fine)

Ebay sells cheap diy solutions just bring your own flashlight. Best to be consistent as others have mentioned your method adds many more variables and you may end up more confused or unable to pin down issues.

Good luck

 

[miha]

Two rolls will not be sufficient to determine consistency of shutter speeds at various speeds across two lenses. 20 rolls of film would be a more realistic plan.

I don't understand why you think it would not be sufficient: 6 frames for one lens (from 1/500s down to 1/15), 6 for another lens, and the second roll for the large format lens using a 6x7 roll-film back offering 10 shots (from 1/500s down to 1s).

If the shots from a particular lens appear equally exposed, I would assume the shutter speeds are consistent.

 

[miha]

This assumes all the shutter speeds are correct in the first place

Indeed it does, at least the middle speeds (1/60 - 1/250) as these have been previously used with slide film. At this point I'm interested in the consistency across shutter speeds for each lens I test.

 

[retina_restoration]

Consider this as an option: Shutter Speed Tester for iOS

 

[Nitroplait]

Consider this as an option: Shutter Speed Tester for iOS

This app is more or less a simplified version of the Audacity approach mentioned early in the thread.

It works reasonably on its own on mid to lower speeds, but much better if you get the PhotoPlug sold by the manufacturer Filmomat.

I think the price for the PhotoPlug is offensive for what it is, but considering the cost of film involved in OP's testing project, it may be justifiable.

The PhotoPlug is just a phototransistor and a resistor soldered onto a TRRS 3.5mm plug and can be easily made at home without violating anyones intellectual property - there is nothing novel involved.

This is how mine looks inside.

 

[BrianShaw]

@miha Your plan should work fine so long as you don't expect scientifically valid results, which I suspect you already don't. Call it a screening study...

Please let us know what you learned!

 

[Chan Tran]

I use the Minolta Booster sensor and an oscilloscope.

 

[Dan Daniel]

I'm testing three leaf shutters: two MamiyaSekor lenses with Seiko Shutters and one Schneider lens in a Compur shutter to check exposure consistency across shutter speeds. I'm not trying to confirm if 1/500 is truly 1/500 etc, but rather if it behaves as one stop faster than 1/250, which should be one stop faster than 1/125, and so on. I’ll shoot a uniformly lit white wall and compare exposures, e.g., 1/500 at f/4 should match 1/250 at f/5,6 if the speeds are evenly spaced. For the Mamiya lenses, I’ll use one roll of 120, testing six speeds per lens from 1/500 to 1/15 (I don't need to go lower since I usae the camera mostly hand-held). For the Schneider lens, I’ll use a second roll in a roll-film back, testing down to 1 second (10 shots available). Both rolls will be developed together. Does this approach seem sound, or am I missing something?

The one thing to watch out for is that judging density variance by eye can be hard. One thing is to use something like a yellow filter to turn colors very similar. this will make density variances more obvious.

Although I understand all the suggestions for shutter speed testers, methods, etc., what you propose could be an interesting experiment if only to show you how subtle variances can be.

 

[miha]

Thank you @BrianShaw and @Dan Daniel

I will present the results here once completed.

 

[koraks]

I don't understand why you think it would not be sufficient: 6 frames for one lens (from 1/500s down to 1/15), 6 for another lens, and the second roll for the large format lens using a 6x7 roll-film back offering 10 shots (from 1/500s down to 1s).

You can't verify consistency at one shot per speed.

If the shots from a particular lens appear equally exposed, I would assume the shutter speeds are consistent.

Yup, but if they're not, you're still none the wiser. Hence my suggestion to just go out and shoot/have fun, as that'll get you pretty much at the same point as the grey wall shots will get you. The former is definitely more fun!

Figuring this out in Audacity probably takes less time than expose & process the 2 rolls of film you intend.

 

[miha]

You can't verify consistency at one shot per speed.

You're right, one shot isn't enough to check consistency. But if that one shot looks good, it'll give me some peace of mind. If it's off, I’ll definitely dig deeper.


That said… statistically speaking, how many shots do I need to hit a decent confidence interval? Asking for a friend.

Yup, but if they're not, you're still none the wiser. Hence my suggestion to just go out and shoot/have fun, as that'll get you pretty much at the same point as the grey wall shots will get you. The former is definitely more fun!

Fair point! For me though, the fun starts when I feel confident (or at least I imagine I know what I’m doing ). Then I can enjoy shooting without second-guessing every exposure. Especially when I’m about to crack open a few of my remaining rolls of Fuji Provia

Figuring this out in Audacity probably takes less time than expose & process the 2 rolls of film you intend.

Not for me, sorry-

 

[koraks]

That said… statistically speaking, how many shots do I need to hit a decent confidence interval? Asking for a friend.

LOL! Well, let's decide on an acceptable p-value first; shall we go for p=.01? Surely we can't get away with .05 anymore, these days!

Well, evidently, do as you see fit. Your plan should work and indeed confirm (at least with decent reliability) a 'true positive' even if it might leave you in the dark on other combinations. If that's all you want/need at this point and you don't mind burning two rolls of film, by all means go ahead.

Personally, I'd really time those shutters. The question isn't if they're off - the question is by how far, approximately.

 

[acrobatic_citron]

Some new gen options from eBay just for completeness. Good luck on your quest

Option 1

Option 2

 

[Chan Tran]

LOL! Well, let's decide on an acceptable p-value first; shall we go for p=.01? Surely we can't get away with .05 anymore, these days!

Well, evidently, do as you see fit. Your plan should work and indeed confirm (at least with decent reliability) a 'true positive' even if it might leave you in the dark on other combinations. If that's all you want/need at this point and you don't mind burning two rolls of film, by all means go ahead.

Personally, I'd really time those shutters. The question isn't if they're off - the question is by how far, approximately.

I generally test focal plane shutter and for doing that the smaller the sensor the better and the output is better the on/off type that is it detects whether the curtain is in front of the sensor or not. With leaf shutter I've been trying for find larger sensor and with analog output. I need the analog output at the highest output doesn't get to the saturation point so that at that point the shutter is fully opened. I need to see the slope of the shutter opening and closing. I have not found satisfactory sensor for this.

 

[MattKing]

In case you haven't been thinking this way....
If you are concerned about consistency, you really need to check results over time, and under the variety of conditions that may present themselves - temperature, humidity, phases of the moon - where consistency might matter.

 

[miha]

Basically everything short of the mood of the darkroom ghost!

 

[BrianShaw]

Given the rather generous tolerances allowable for shutter speeds, it seems that tight statistical measures are not necessary. A commonly accepted sample size for “minimal reasonable statistical validity” is seven (7). But the proposed screening study will definitely help identify if there’s reason to do further study or not.

The only question I’d be asking myself in this situation is how much difference would I consider reasonably acceptable. My answer would be in the 1/3 to 2/3 stop range.

 

[miha]

Good luck on your quest

Thank you.

 

[ic-racer]

I'm testing three leaf shutters: two MamiyaSekor lenses with Seiko Shutters and one Schneider lens in a Compur shutter to check exposure consistency across shutter speeds. I'm not trying to confirm if 1/500 is truly 1/500 etc, but rather if it behaves as one stop faster than 1/250, which should be one stop faster than 1/125, and so on. I’ll shoot a uniformly lit white wall and compare exposures, e.g., 1/500 at f/4 should match 1/250 at f/5,6 if the speeds are evenly spaced. For the Mamiya lenses, I’ll use one roll of 120, testing six speeds per lens from 1/500 to 1/15 (I don't need to go lower since I usae the camera mostly hand-held). For the Schneider lens, I’ll use a second roll in a roll-film back, testing down to 1 second (10 shots available). Both rolls will be developed together. Does this approach seem sound, or am I missing something?

Yes, film exposures are the best. Otherwise, the flux at the film plane is only estimated with leaf shutter testers.

 

[runswithsizzers]

You can't verify consistency at one shot per speed.

As others have suggested, any testing procedure must evaluate not only accuracy, but also precision. Any comparrison of 1/125th second to 1/250th second is meaningless until you know how much variaion there is at 1/125th second. If 10 exposures at 1/125th second vary by +/- one f-stop, then sometimes 1/125th is 1/250th and sometimes 1/125th is 1/60th.

Hopefully, the variation will be smaller than that, but you won't know until you have measured it.

That said… statistically speaking, how many shots do I need to hit a decent confidence interval? Asking for a friend.

When I was working in a clinical lab, we liked to have at least 20 replicates before trying to define precision for most measured results.

 

[F4U]

I recall in The Amateur Photographers Handbook by Aaron Sussman was depicted a Haynes Shutter Checker, I believe it was called. It was supposedly a phonograph disc that is set in motion and shot on film. I would think the object was to measure the angle of the motion-blurred image and calculate the shutter speed. Of course, those books date back to heaven-knows-when, most likely to be run on the 78rpm record players of the day, which were likely not highly accurate. Today there are strobes and DC motors allowing you to get turntable speed dead-on the money. If you don't mind burning up a few rolls of film, I bet it is still and excellent way to check shutter speeds. But now you can get cheap USB testers off ebay, which work very well on speeds below 1/50, but not so well on faster speeds of leaf shutters. So you'd use the USB tester for slow, and switch over to the Haynes on the faster ones, using up less film. Of course where are you going to find an old Haynes checker?