Re: Leaf Shutter High Speed
Have you asked reversal film how well your leaf shutters' high speeds work?
Re: Leaf Shutter High Speed
Here’s an Alphax 5 shutter opening and closing nice and slow: https://alphaxbetax.files.wordpress....lades-demo.mov
Re: Leaf Shutter High Speed
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.
Re: Leaf Shutter High Speed
Quote:
Originally Posted by
Dan Fromm
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.
Quote:
Originally Posted by
Whir-Click
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?
Quote:
Originally Posted by
Robert Tilden
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:
Re: Leaf Shutter High Speed
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.
Re: Leaf Shutter High Speed
“ 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.
Re: Leaf Shutter High Speed
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.
Re: Leaf Shutter High Speed
Quote:
Originally Posted by
Eric Woodbury
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.
Quote:
Originally Posted by
Whir-Click
“ 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.
Quote:
Originally Posted by
Eric Woodbury
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.
Quote:
Originally Posted by
Bob Salomon
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.
Re: Leaf Shutter High Speed
Love my PQS Schneider lenses. 1/1000 is a lot more useful than you might think (at least in Medium Format).