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gnd2
8-Aug-2020, 11:10
Long post for anyone interested in geeking out for a bit. If you think high shutter speed are irrelevant because we should always stop down to maximize DOF and only use slow shutter speeds, this may not be of interest to you. No need to comment, just enjoy the scenery :) I would actually like to use the faster speeds, and as I've been checking out the used lenses I've been buying, the phenomenon of the fast speeds measuring much slower than their labelled speed piqued my curiosity.

I've been doing a lot of searching to understand this, but my tests don't quite match up with what I've been reading.

Let's start with the basic shutter speed tester: phototransistor to detect the opening and closing of the shutter and measuring the elapsed time. Works great at slow shutter speeds where the time it takes for the shutters to transition is insignificant compared to the time the shutter is open, so the shutter is effectively fully open for the entire shutter duration. But at faster speeds (say about 1/125 and faster), the shutter transition time becomes significant.

At the fastest speed, using the basic shutter tester, people will typically measure a speed roughly half of the labelled speed. The claim is that this is because the tester measures from when the shutter first starts opening to when it's completely closed, but since it takes time for the shutter blades to transition from fully open to fully closed, they start closing again as soon as they're fully open. So if you integrate the light intensity over the entire time, it's actually 1/2 what it would be if the shutter transition where instantaneous. Therefore, if the shutter takes 1/200 from start to finish, the effective exposure is equivalent to 1/400.

Soooooo...

I made the basic shutter tester with an Arduino Uno and phototransistor. And sure enough, at the fastest speed (1/400 on all the lenses I've tested), the measured speed is roughly 1/200. So I decided to hook the phototransistor up to the ADC to try and plot the opening and closing of the shutter and see if it matched the claim. At the 1/400 setting I get this:

206701


I got similar results with several different lenses / shutters - LF with Copal and RB67 lenses. Seems that it really is slow, but it's so common, why would the manufactures label them as being faster? At least it's only about a stop over exposed which isn't too bad with negative film. I'm still curious what's actually going on here. I'd really like to see a slow motion video of the shutter. There are plenty of focal plane shutter videos, but I haven't found a good leaf shutter video.

Dan Fromm
8-Aug-2020, 11:39
Have you asked reversal film how well your leaf shutters' high speeds work?

Whir-Click
8-Aug-2020, 14:01
Here’s an Alphax 5 shutter opening and closing nice and slow: https://alphaxbetax.files.wordpress.com/2019/01/shutter-blades-demo.mov

Robert Tilden
8-Aug-2020, 14:32
Depending on the phototransistor it may be acting more like a switch than providing an analog signal proportional to light falling on it. For fast shutter speeds the 'plateau' of a fully opened shutter may be quite short, so the opening and closing 'ramp' will be a significant portion of the total exposure. If the phototransistor triggers early in the shutter cycle the graph would not be showing an accurate representation of the effective shutter speed.

gnd2
8-Aug-2020, 15:58
Have you asked reversal film how well your leaf shutters' high speeds work?
I have not. I was hoping to avoid having to burn film to test all my lenses. I may have to, but it's become more about my curiosity of what's actually happening than simply the practical question of what the actual speeds are.


Here’s an Alphax 5 shutter opening and closing nice and slow: https://alphaxbetax.files.wordpress.com/2019/01/shutter-blades-demo.mov
Thanks, but is that actually a slow motion video at the fastest shutter speed, or is it being manually opened and closed in real-time?


Depending on the phototransistor it may be acting more like a switch than providing an analog signal proportional to light falling on it. For fast shutter speeds the 'plateau' of a fully opened shutter may be quite short, so the opening and closing 'ramp' will be a significant portion of the total exposure. If the phototransistor triggers early in the shutter cycle the graph would not be showing an accurate representation of the effective shutter speed.

I thought about that, it's actually one of my biggest concerns about my testing method at this point. I believe I have it calibrated so that is not the case. The ADC data is not quite reaching full scale and it varies depending on how close the lens/light is to the phototransistor. It's a bpw77na if you're interested.

I'm wondering if there's a way I could test with my flash meter... :confused:

Eric Woodbury
8-Aug-2020, 16:12
As Robert noted, phototransistors are not to be trusted for evaluation of amplitude. Depending on the circuit, transistor, etc., linearity is not the best. For absolute amplitude, a photodiode is required. At these speeds, rise/fall times of transistor should be ok, but this depends on the load and capacitance. A garden variety phototransistor is about 25 pF.

Over the years, I've measured my shutters, some of them brand new, on an occasional basis. Here are those numbers for 1/500 and 1/400 (should be 2 and 2.5 milliseconds, respectively):

1/500: 2.5, 2.5, 2.5, 5.0, 3.6, 3.7, 3.4, 3.6, 3.4
1/400: 4.3, 4.5, 5.0, 5.0, 5.1, 5.5

Moving the shutter to the top position really tightens the shutter spring and it doesn't feel good. I seldom use anything above 1/60.

Whir-Click
8-Aug-2020, 16:32
“ Thanks, but is that actually a slow motion video at the fastest shutter speed, or is it being manually opened and closed in real-time?”

Opened and closed manually in real time with the preview lever to illustrate the action. I’m curious what you would be looking for in a slow motion video of a leaf shutter’s fastest speed.

Bob Salomon
8-Aug-2020, 17:04
American Traffic Systems needed a medium format camera with a leaf shutter that could operate at its highest speeds so it would synch with strobe for their traffic cameras. They chose the Hasselblad EL cameras with their latest Prontor shutters. Once in service they found that after a couple of shots at 1/500 the shutters broke down.
So they contacted us and bought Rollei 6008 cameras with the PQS linear motor leaf shutters with carbon fiber blades that could reach a true 1/1000. They installed the first system in the backwoods of Australia and contacted us to let us know that after 100,000 exposures at 1/1000 they had no failures. A mechanical shutter could not reach 1/500 and could not reliably operate continuously at that speed. The spring would break.
The Rollei shutter had no springs.

gnd2
8-Aug-2020, 17:13
As Robert noted, phototransistors are not to be trusted for evaluation of amplitude. Depending on the circuit, transistor, etc., linearity is not the best. For absolute amplitude, a photodiode is required. At these speeds, rise/fall times of transistor should be ok, but this depends on the load and capacitance. A garden variety phototransistor is about 25 pF.
Well that's disappointing. I found some info about using a photodiode, maybe I'll have a go at that some day.


“ Thanks, but is that actually a slow motion video at the fastest shutter speed, or is it being manually opened and closed in real-time?”

Opened and closed manually in real time with the preview lever to illustrate the action. I’m curious what you would be looking for in a slow motion video of a leaf shutter’s fastest speed.
Wanted to see if it actually started closing immediately after it reached full open or it if stayed open for a while as my plot suggests.


Moving the shutter to the top position really tightens the shutter spring and it doesn't feel good. I seldom use anything above 1/60.

American Traffic Systems needed a medium format camera with a leaf shutter that could operate at its highest speeds so it would synch with strobe for their traffic cameras. They chose the Hasselblad EL cameras with their latest Prontor shutters. Once in service they found that after a couple of shots at 1/500 the shutters broke down.
So they contacted us and bought Rollei 6008 cameras with the PQS linear motor leaf shutters with carbon fiber blades that could reach a true 1/1000. They installed the first system in the backwoods of Australia and contacted us to let us know that after 100,000 exposures at 1/1000 they had no failures. A mechanical shutter could not reach 1/500 and could not reliably operate continuously at that speed. The spring would break.
The Rollei shutter had no springs.
:( Maybe I ought to stay away from the fastest speeds after all.

6x6TLL
8-Aug-2020, 17:47
Love my PQS Schneider lenses. 1/1000 is a lot more useful than you might think (at least in Medium Format).

EH21
8-Aug-2020, 19:56
That's cool information to read, thanks!

American Traffic Systems needed a medium format camera with a leaf shutter that could operate at its highest speeds so it would synch with strobe for their traffic cameras. They chose the Hasselblad EL cameras with their latest Prontor shutters. Once in service they found that after a couple of shots at 1/500 the shutters broke down.
So they contacted us and bought Rollei 6008 cameras with the PQS linear motor leaf shutters with carbon fiber blades that could reach a true 1/1000. They installed the first system in the backwoods of Australia and contacted us to let us know that after 100,000 exposures at 1/1000 they had no failures. A mechanical shutter could not reach 1/500 and could not reliably operate continuously at that speed. The spring would break.
The Rollei shutter had no springs.

reddesert
8-Aug-2020, 20:49
Long post for anyone interested in geeking out for a bit. If you think high shutter speed are irrelevant because we should always stop down to maximize DOF and only use slow shutter speeds, this may not be of interest to you. No need to comment, just enjoy the scenery :) I would actually like to use the faster speeds, and as I've been checking out the used lenses I've been buying, the phenomenon of the fast speeds measuring much slower than their labelled speed piqued my curiosity.

I've been doing a lot of searching to understand this, but my tests don't quite match up with what I've been reading.

Let's start with the basic shutter speed tester: phototransistor to detect the opening and closing of the shutter and measuring the elapsed time. Works great at slow shutter speeds where the time it takes for the shutters to transition is insignificant compared to the time the shutter is open, so the shutter is effectively fully open for the entire shutter duration. But at faster speeds (say about 1/125 and faster), the shutter transition time becomes significant.

At the fastest speed, using the basic shutter tester, people will typically measure a speed roughly half of the labelled speed. The claim is that this is because the tester measures from when the shutter first starts opening to when it's completely closed, but since it takes time for the shutter blades to transition from fully open to fully closed, they start closing again as soon as they're fully open. So if you integrate the light intensity over the entire time, it's actually 1/2 what it would be if the shutter transition where instantaneous. Therefore, if the shutter takes 1/200 from start to finish, the effective exposure is equivalent to 1/400.



This gets discussed in roughly every thread about shutter testing. If one puts the phototransistor directly behind the lens on-axis, or if one puts the phototransistor on axis behind a naked shutter w/o lens elements, it "sees" light from the first instant the shutter opens a little bit at the center, to the last instant it closes. So it doesn't compensate for the "shutter efficiency" where the shutter is open across the outer parts of the pupil for a much shorter time.

Putting the sensor well behind the lens at the focal plane and illuminating the lens uniformly from the front may show a slower ramp up, but you do still have to worry about whether the phototransistor is linear or a switch as someone else mentioned.

Havoc
9-Aug-2020, 06:33
I wonder what the result would be if you compare a normal Compur with an electronically controlled one like in a Fuji GX680 or Bronica.

Robert Tilden
9-Aug-2020, 08:26
You might also test at various apertures. I recently read a paper that claimed that leaf shutters were more 'efficient' at smaller apertures. The reasoning being (I think) that the shutter clears/occludes the smaller aperture faster. There is also a ramp up/dwell/ramp down cycle in the shutter action that might make faster speeds somewhat more challenging to measure- the dwell portion may be quite short compared to the open/close times. I think this is one reason a high speed video would be interesting...

mmerig
9-Aug-2020, 09:31
Depending on the phototransistor it may be acting more like a switch than providing an analog signal proportional to light falling on it. For fast shutter speeds the 'plateau' of a fully opened shutter may be quite short, so the opening and closing 'ramp' will be a significant portion of the total exposure. If the phototransistor triggers early in the shutter cycle the graph would not be showing an accurate representation of the effective shutter speed.

In the shutter tester I built, I use a phototransistor (a Vishay BPW85B) and it detects pulsed light through the lens at 10K Hz. There is a dramatic difference in amplitude in the signal representing this pulsing during the time the shutter is open. Here is an example of the signal for 1/100 sec. The opening and closing parts of the shutter action are visible. The entire opening time is 1/111 s. Without the ramping up and down, it is 1/114 s. The stop was f8.

The capacitance for the phototransistor at the voltage I run it at (9 VDC, C to E)) is 2.5 pF -- very small. The bandwdith is about 180 KHz

I read the voltage with a sound card, which only goes to 20K Hz. I set the 555 timer to 10K Hz so that I would have double the bandwidth to better capture the signal.

206726

The signal is more than precise enough to capture the shutter action.

Bob Salomon
9-Aug-2020, 09:38
I wonder what the result would be if you compare a normal Compur with an electronically controlled one like in a Fuji GX680 or Bronica.

If it is spring driven with conventional blades it will be essentially the same.

Dan Fromm
9-Aug-2020, 10:04
Mike, I could be mistaken but I don't believe that a Supermatic opens and closes as fast -- in 0.000237079 seconds combined -- as your measurements show.

gnd2
9-Aug-2020, 13:13
This gets discussed in roughly every thread about shutter testing. If one puts the phototransistor directly behind the lens on-axis, or if one puts the phototransistor on axis behind a naked shutter w/o lens elements, it "sees" light from the first instant the shutter opens a little bit at the center, to the last instant it closes. So it doesn't compensate for the "shutter efficiency" where the shutter is open across the outer parts of the pupil for a much shorter time.

Putting the sensor well behind the lens at the focal plane and illuminating the lens uniformly from the front may show a slower ramp up, but you do still have to worry about whether the phototransistor is linear or a switch as someone else mentioned.

Thanks for this. I've read quite a few threads but don't recall ever seeing this bit of information.

I diffused the light going into the lens and placed the sensor near the focal distance of the lens and got this:

206734

Not perfect, but much closer to expected. Close enough for me to chalk up the difference to experimental error (a lot of eyeballing going on) and satisfy my curiosity.

mmerig
9-Aug-2020, 22:21
Mike, I could be mistaken but I don't believe that a Supermatic opens and closes as fast -- in 0.000237079 seconds combined -- as your measurements show.

I agree, the time difference is very small may probably wrong, but I am not sure why. It could easily be 2X the 0.0002 measure, as 10 KHz cycle is 0.0001 s.

My measurements could be biased to the len's central axis, as reddesert mentions in post #12. The lens elements remain on the shutter, but the pulsing LED is about an inch from the front of the lens, and the phototransistor is within a 1/4 inch of the rear element. I do it this way to make sure I get a high signal-to-noise ratio. The light is so out of focus though, that the on-axis effect is probably negligible. The light circle on a surface very near the rear lens element (as close as I can get it and still see it) is about the same size as the rear element, so we are not dealing with a narrow light source at the sensor location.

What I was mainly trying to show is that the phototransistor response is fast enough to capture a 10 KHz rise and fall, and using pulsed light gives a more intuitive sense of the shutter opening and closing, and finally, amplitude linearity is not that important when interpreting a pulsed-light signal.

Measuring the phototransistor's voltage amplitude linearity to light amplitude would be worthwhile (the device's datasheet does not show this), and may not be that hard to do, so I may try it. The other aspect is the angle of sensitivity -- it's +- 25 degrees for 50% sensitivity for the device I am using, so off-center light is detected (but the angle is reduced by the entrance hole in the transistor mount). I could get a sense of the on-axis effect by moving the sensor off-axis and see what happens.

I get good exposures using my corrected shutter speeds, and I mostly use slow speeds and f-stops of 16 to 22, so never was that concerned with shutter efficiency.

Havoc
10-Aug-2020, 08:23
Thanks for this. I've read quite a few threads but don't recall ever seeing this bit of information.

I diffused the light going into the lens and placed the sensor near the focal distance of the lens and got this:

206734

Not perfect, but much closer to expected. Close enough for me to chalk up the difference to experimental error (a lot of eyeballing going on) and satisfy my curiosity.

I find this an interesting curve. It is indeed more what you would expect. Could you please give the horizontal axis and what setting the shutter was set at?

Doremus Scudder
10-Aug-2020, 10:10
Robert's comment about aperture size is quite relevant here. At a fast shutter speed where the opening/closing of the leaf shutter takes so much of the total "open time," the efficiency will be markedly different between a wide-open aperture (least efficient) and a very small aperture (most efficient). I would think it would be important to do your shutter testing at the aperture(s) you use most.

I know that I rarely, if ever, make a photograph at an aperture smaller than f/22. I'd say more than half of my exposures are made at an aperture somewhere around f/32 (give or take a third of a stop), so I'd likely test at f/32.

Having some way to measure the total volume of light instead of just the time between the first glimmer of light to make it through the opening shutter and the instant it goes dark would seem to be necessary to really get meaningful exposure data with a leaf shutter at high speeds. Maybe Dan's suggestion about asking your reversal/transparency film is going to end up being the most practical after all...

Best,

Doremus

gnd2
10-Aug-2020, 10:31
I find this an interesting curve. It is indeed more what you would expect. Could you please give the horizontal axis and what setting the shutter was set at?

Horizontal axis is sample number. Sample rate is about 9615.3846 samp/sec. ADC is in free-run mode, 16 MHz clock source / 128 prescaler / 13 clock cycles per conversion.

Lens was a Mamiya Sekor C 127mm, wide open at f/3.8 and 1/400 shutter speed (it's fastest setting).

Havoc
10-Aug-2020, 12:05
Horizontal axis is sample number. Sample rate is about 9615.3846 samp/sec. ADC is in free-run mode, 16 MHz clock source / 128 prescaler / 13 clock cycles per conversion.

Lens was a Mamiya Sekor C 127mm, wide open at f/3.8 and 1/400 shutter speed (it's fastest setting).

Ok, so about 0.0001s between samples and your shutter time should be 0.0025s or 25 samples. Now if you take that the slopes are about symmetrical around the 100 level (50% level) then for "total light" if you measure between the 50% points you get something like 38 samples or 1/263s. A bit faster than half speed. Very rough from the graph on the screen.

gnd2
10-Aug-2020, 13:03
Ok, so about 0.0001s between samples and your shutter time should be 0.0025s or 25 samples. Now if you take that the slopes are about symmetrical around the 100 level (50% level) then for "total light" if you measure between the 50% points you get something like 38 samples or 1/263s. A bit faster than half speed. Very rough from the graph on the screen.

Yes, but this is still an imperfect measurement. As the measurement improves, the slopes lean in towards each other making a tighter peak at the top. Assuming a perfect measurement would be very close to an ideal triangle, the effective shutter speed would be 1/2 the total time.

For the total time, extrapolate the linear approximation of the slopes down to 0 amplitude and determine the time between those points. It's tends to hover around 1/180.
As the slopes approach an ideal peak, the 50% level approaches 1/2 that, or 1/360. Close enough to 1/400 for rock and roll, eh?

As you stop down from wide open, the effective shutter speed would decrease from 1/360 to nearly 1/180 (the actual shape with the aperture closed down would start to look like the plots I have).

Eric Woodbury
10-Aug-2020, 16:04
The "half-max" levels are not well-known here as the photo sensor is probably acting as a switch and certainly not linear between OFF and ON. Perhaps the 'switch' is fast enough and this doesn't matter, or perhaps the rise time is dominated by the RC time constant of the circuit. A way to check is to measure the ON time of a strobe flash. Strobes have extremely fast risetimes.

If the photo sensor were a photodiode and the circuit a TIA, then the data would hold useable amplitude information.

gnd2
10-Aug-2020, 19:21
The "half-max" levels are not well-known here as the photo sensor is probably acting as a switch and certainly not linear between OFF and ON. Perhaps the 'switch' is fast enough and this doesn't matter, or perhaps the rise time is dominated by the RC time constant of the circuit. A way to check is to measure the ON time of a strobe flash. Strobes have extremely fast risetimes.

If the photo sensor were a photodiode and the circuit a TIA, then the data would hold useable amplitude information.

I took your previous post at face value because I didn't want to get into the device characteristics, but since you've mentioned it again...

No, it's not acting as a switch. It's wired in a common collector configuration with the emitter resistor value set to keep it in the active region up to the maximum light intensity received. So it is actually pretty linear, except obviously near dark, which you can see in the plots.

It should be obvious from the first plot that the response time is plenty fast enough for our purposes.

mmerig
10-Aug-2020, 21:57
Yes, but this is still an imperfect measurement. As the measurement improves, the slopes lean in towards each other making a tighter peak at the top. Assuming a perfect measurement would be very close to an ideal triangle, the effective shutter speed would be 1/2 the total time.

For the total time, extrapolate the linear approximation of the slopes down to 0 amplitude and determine the time between those points. It's tends to hover around 1/180.
As the slopes approach an ideal peak, the 50% level approaches 1/2 that, or 1/360. Close enough to 1/400 for rock and roll, eh?

As you stop down from wide open, the effective shutter speed would decrease from 1/360 to nearly 1/180 (the actual shape with the aperture closed down would start to look like the plots I have).

Why would a perfect measurement be necessarily triangular? This could be so for very fast shutter speeds, but not for slower ones (say 1/30 s or slower), unless the blades opening and closing time is proportional to the shutter speed, which would be a lousy shutter. Eventually, with a higher sampling rates, and good linearity,the shape of the curve would stabilize, and it could have a flat top.

The second graph you have may be pretty close to reality. The system you have seems well thought-out, and you have most of the bases covered.

gnd2
10-Aug-2020, 23:56
Why would a perfect measurement be necessarily triangular? This could be so for very fast shutter speeds, but not for slower ones (say 1/30 s or slower), unless the blades opening and closing time is proportional to the shutter speed, which would be a lousy shutter. Eventually, with a higher sampling rates, and good linearity,the shape of the curve would stabilize, and it could have a flat top.
I was referring specifically to the fastest shutter speed with the triangle comment. At the fastest speed, it starts closing again as soon as it reaches fully open, so a triangle. At slower speeds it lingers fully open for a period of time before closing and becomes trapezoidal. The slope remains the same, but as the shutter speed decreases, the time between open and close gets longer and the slope becomes less significant.

mmerig
11-Aug-2020, 07:35
Thanks, I did not realize you were referring to the fastest shutter speeds only.

Maybe I am missing something, but I wonder why manufacturers don't publish shutter efficiencies or the graphs themselves for their shutters. There is plenty on lens performance. Even Ansel Adam's "The Camera" book has only a theoretical graph demonstrating shutter efficiency (although he does report a range of efficiencies). Digital storage oscilloscopes have been around since the 1980's, and something like this could have been used to do the job.

Andy Eads
11-Aug-2020, 10:32
The efficiency of the shutter plays into all this. The 1960 edition of the Focal Encyclopedia of Photography defines it as the ratio of the light (the shutter) transmits during the exposure to the amount that it would transmit if it were fully open for the whole duration of the exposure. So a shutter might be open for 1/500 sec. but only transmit the amount of light expected at 1/1000 sec. That shutter would be 50% efficient. The rate of speed the blades or curtains can achieve is the limiting factor. Lower mass blades and higher force improve efficiency. The PQS shutter Bob Salomon cited is a fine example of a high efficiency shutter. In a 50% efficient shutter, lots of activity can be going on that would register as exposure, negating the usefulness of the 1/1000 sec. shutter speed for many applications. My memory is foggy here but Zeiss made a very efficient leaf shutter for its aerial survey cameras by having multiple rotating blades that did not "uncap" till they were up to speed. I remember the surprise I had as a 14 year old seeing the stopping power of a short-duration electronic flash compared to what was possible with ordinary shutters.

Bob Salomon
11-Aug-2020, 11:03
The efficiency of the shutter plays into all this. The 1960 edition of the Focal Encyclopedia of Photography defines it as the ratio of the light (the shutter) transmits during the exposure to the amount that it would transmit if it were fully open for the whole duration of the exposure. So a shutter might be open for 1/500 sec. but only transmit the amount of light expected at 1/1000 sec. That shutter would be 50% efficient. The rate of speed the blades or curtains can achieve is the limiting factor. Lower mass blades and higher force improve efficiency. The PQS shutter Bob Salomon cited is a fine example of a high efficiency shutter. In a 50% efficient shutter, lots of activity can be going on that would register as exposure, negating the usefulness of the 1/1000 sec. shutter speed for many applications. My memory is foggy here but Zeiss made a very efficient leaf shutter for its aerial survey cameras by having multiple rotating blades that did not "uncap" till they were up to speed. I remember the surprise I had as a 14 year old seeing the stopping power of a short-duration electronic flash compared to what was possible with ordinary shutters.

The LInhof Aerotronica 70mm aerial roll film camera had a rotary shutter that went to 1/1500. However it required 24V aircraft current and was only hand directable with bungee straps to the empty helicopter doorway.

mmerig
11-Aug-2020, 19:15
The efficiency of the shutter plays into all this. The 1960 edition of the Focal Encyclopedia of Photography defines it as the ratio of the light (the shutter) transmits during the exposure to the amount that it would transmit if it were fully open for the whole duration of the exposure. So a shutter might be open for 1/500 sec. but only transmit the amount of light expected at 1/1000 sec. That shutter would be 50% efficient. The rate of speed the blades or curtains can achieve is the limiting factor. Lower mass blades and higher force improve efficiency. The PQS shutter Bob Salomon cited is a fine example of a high efficiency shutter. In a 50% efficient shutter, lots of activity can be going on that would register as exposure, negating the usefulness of the 1/1000 sec. shutter speed for many applications. My memory is foggy here but Zeiss made a very efficient leaf shutter for its aerial survey cameras by having multiple rotating blades that did not "uncap" till they were up to speed. I remember the surprise I had as a 14 year old seeing the stopping power of a short-duration electronic flash compared to what was possible with ordinary shutters.

There seems to be a contradiction here. Although "there is lots of activity going on" with a 50% efficient shutter, such activity leads to less exposure than if the shutter was 100% efficient, as you mention earlier, so a 1/1000 s speed could still be useful, and even faster.

Your surprise reminds me of when I was a kid, I made a switch out of a can with a balloon stretched over it, like a drum, with foil that actuated an electronic flash. I made pictures of glass bottles shattering as the sound actuated the flash. The shutter was set on B or T, and the bottle was in the dark.

Havoc
11-Aug-2020, 23:32
Let's keep it to mechanical leaf shutters. Otherwise we could wander to Faraday/Kerr cell shutters and other fancy stuff like that. Or Eg&G Microflashes.

JimboWalker
21-Aug-2020, 19:19
Do not rely on higher speed markings!! All of my newer and older shutters are generally one stop slower than marked. Carol Miller at Flutots' repair ( The Best!!) tuned up a Linhof Synchro-Compur for me a month or so ago. 4ooth of sec. is one stop slow. All of the slower speeds are almost right on! In practical use, stay away from counting on higher speed accuracy with any leaf shutter. My Rollei TLR shutter is similar. I never use a shutter speed higher than 60th sec. on my large format anyway, so who cares. The science is informative, but of little practical use in the field.