TESTING the various shutter speeds on a 1950 Rolleiflex camera.

Thread Starter

273greg

Joined Mar 24, 2021
7
I inherited this beautiful 1950 Rolleiflex camera from my father and my friend gave me his 1954 Heathkit oscilloscope. I am a newbie to this testing device and I would like suggestions on basic ways of using a 555 timer plus a phototransistor from a computer mouse to do a shutter speed test. I have read up a little on the designs and I find too many options and variables. The basic idea is to shine a bright light into the lens of the camera, set one of eight different shutter speeds, and release the shutter. When the light hits the sensor and when it stops should show on the scope. This is supposed to show the length of time the shutter was open for. I need some guidance for the simplest (not necessarily the best) set up that I can understand. I would appreciate any and all comments. Thank you, Greg
 

GetDeviceInfo

Joined Jun 7, 2009
1,875
Your scope won’t help you much with this. A modern storage scope could capture the transition, but not your early Heathkit. Watching the scope would be the same as watching the light through the shutter. What you need is a timer/counter, enabled by the photo detector. A 555 would also not be a good choice, but that depends on you4 desired accuracy. A simple Arduino could handle this task admirably.
 

Thread Starter

273greg

Joined Mar 24, 2021
7
thankyou for your input, I will need accuracy eventually, but first need to get set up and started. I guess I should buy myself an Adrduino, Is $25 ok to spend on one? are you saying that if I made a 555 circuit, I will get poor results? If I can prove accurate shutter speeds to the buyer, I can ask $500 to $1000 more than an as-is camera.
 

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Yaakov

Joined Jan 27, 2019
3,464
thankyou for your input, I will need accuracy eventually, but first need to get set up and started. I guess I should buy myself an Adrduino, Is $25 ok to spend on one? are you saying that if I made a 555 circuit, I will get poor results? If I can prove accurate shutter speeds to the buyer, I can ask $500 to $1000 more than an as-is camera.
OK, first of all, that scope doesn't even have a reticle so you aren't going to be able to use it for measurements.

There are several ways you can use an Arduino, or a compatible board, to do the timing to a reasonable degree of accuracy. If it is a genuine Arduino board or something like a Teensy 4.1, ~$25 is a good price.

The 555 is not a particularly good choice for this.
 

crutschow

Joined Mar 14, 2008
27,696
Unfortunately, that oscilloscope does not have a calibrated sweep speed like newer scopes do, so it's not useful for trying to determine pulse width.
 
This is what I would do. With a 1 Mhz crystal build an oscillator. Feed it to three cascaded decade counters to obtain a 1khz pulse train. Feed it to a transistor to drive several IR LEDs.

Shine them to the lens.
Inside the camera place a photo diode. Its output feed to a DSO set in the one shot mode.
The timebase span should be slightly longer than the expected shutter speed. I.e. for 1/60 second, which means 16.667 milli seconds, set the horizontal scale to 2 milli seconds per division for a total span of 20 milli seconds.

Arm the scope, and trigger the shutter. With the horizontal cursors measure the resulting burst width.
 

MrChips

Joined Oct 2, 2009
24,143
Yes you can do it if you can find or make a known reference oscillator. You can use a 555-timer circuit with a theoretical frequency based on R and C values. A more accurate oscillator would be one using a quartz crystal.

Let us begin with attempting to measure a standard shutter speed of 1/100 second which is 10ms.
If we aim for ±10% resolution then we need to measure to within 1ms. This calls for a 1kHz oscillator as the poster above suggests.

Use the 1kHz reference signal to calibrate your oscilloscope. Set the Hor/Freq and Freq Vernier to get about 20ms across the screen. Mark off on piece of plastic/paper/tape on the face of the scope every 1ms mark. Shine light through the lens to a photo detector and measure the width of the one-shot rectangular wave observed on the screen.

As your oscilloscope cannot capture a one-shot event you will have some difficulty seeing the single sweep when the camera shutter is triggered. With a newer digital or storage scope all of the above is irrelevant.
 

GetDeviceInfo

Joined Jun 7, 2009
1,875
Your most basic Arduino will do this ($5). Where the scope would come in handy is measuring the response of the light detector. Drive it at resolving frequency to confirm if it’s response time is adequate
 

Thread Starter

273greg

Joined Mar 24, 2021
7
This is what I would do. With a 1 Mhz crystal build an oscillator. Feed it to three cascaded decade counters to obtain a 1khz pulse train. Feed it to a transistor to drive several IR LEDs.

Shine them to the lens.
Inside the camera place a photo diode. Its output feed to a DSO set in the one shot mode.
The timebase span should be slightly longer than the expected shutter speed. I.e. for 1/60 second, which means 16.667 milli seconds, set the horizontal scale to 2 milli seconds per division for a total span of 20 milli seconds.

Arm the scope, and trigger the shutter. With the horizontal cursors measure the resulting burst width.
Wow, I am a beginner and if I can do that I won't consider myself a beginner anymore. Thank you very much for you knowledge and input,,, Good health to you, Greg
 

Thread Starter

273greg

Joined Mar 24, 2021
7
Yes you can do it if you can find or make a known reference oscillator. You can use a 555-timer circuit with a theoretical frequency based on R and C values. A more accurate oscillator would be one using a quartz crystal.

Let us begin with attempting to measure a standard shutter speed of 1/100 second which is 10ms.
If we aim for ±10% resolution then we need to measure to within 1ms. This calls for a 1kHz oscillator as the poster above suggests.

Use the 1kHz reference signal to calibrate your oscilloscope. Set the Hor/Freq and Freq Vernier to get about 20ms across the screen. Mark off on piece of plastic/paper/tape on the face of the scope every 1ms mark. Shine light through the lens to a photo detector and measure the width of the one-shot rectangular wave observed on the screen.

As your oscilloscope cannot capture a one-shot event you will have some difficulty seeing the single sweep when the camera shutter is triggered. With a newer digital or storage scope all of the above is irrelevant.
Thank you very much for your wise adivise, I will take all this into consideration,, stay healthy,, Greg
 
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