Measuring focal plane shutter speeds with a turntable and distortion due to the rolling shutter effect

[ic-racer]

How do you test the shutter speed of a digital camera?

Running LED array is one option.

 

[Niglyn]

How do you test the shutter speed of a digital camera?

Proprietary test software. The digital camera already has the sensor, so very easy for test software to monitor when a single pixel sees and does not see light.

As modern cameras are microprocessor controlled, running on a very accurate clock, they can test themselves.

The only simple way that I can think of is a row of LEDs. Each one lights for 1/30s before extinguishing and the next in series turns on.
At a shutter speed of 1/30s, one should see 1 or 2 LEDs lit. Any more and the shutter would be slower than 1/30s.
Next run the LEDs at 1/60s. Again at a shutter speed of 1/60s one should see 1 or 2 LEDs lit.
This can be continued through all the shutter speeds.

Very easy to make, probably £5 in parts or just bits from the scrap-box.

If anyone has any better ideas, I'm happy to have a go at building it.

Some light reading on the subject.

The Way to Modern Shutter Speed Measurement Methods: A Historical Overview - PMC

Exposure time is a fundamental parameter for the photographer when the photo is composed, and the exact length of the exposure may be an essential determinant of performance in certain camera-based applications, e.g., optical camera communication ...

www.ncbi.nlm.nih.gov

 

[Chan Tran]

Proprietary test software. The digital camera already has the sensor, so very easy for test software to monitor when a single pixel sees and does not see light.

As modern cameras are microprocessor controlled, running on a very accurate clock, they can test themselves.

The only simple way that I can think of is a row of LEDs. Each one lights for 1/30s before extinguishing and the next in series turns on.
At a shutter speed of 1/30s, one should see 1 or 2 LEDs lit. Any more and the shutter would be slower than 1/30s.
Next run the LEDs at 1/60s. Again at a shutter speed of 1/60s one should see 1 or 2 LEDs lit.
This can be continued through all the shutter speeds.

Very easy to make, probably £5 in parts or just bits from the scrap-box.

If anyone has any better ideas, I'm happy to have a go at building it.

Some light reading on the subject.

The Way to Modern Shutter Speed Measurement Methods: A Historical Overview - PMC

Exposure time is a fundamental parameter for the photographer when the photo is composed, and the exact length of the exposure may be an essential determinant of performance in certain camera-based applications, e.g., optical camera communication ...

www.ncbi.nlm.nih.gov

But then the shutter is going away in digital camera so it may not be relevant much longer. I wonder now if we can get our hands on those Kyoritsu shutter testers as repair shops for film cameras close down.

 

[Niglyn]

But then the shutter is going away in digital camera so it may not be relevant much longer. I wonder now if we can get our hands on those Kyoritsu shutter testers as repair shops for film cameras close down.

You will be lucky. In the noughties maybe, but now anything film related has sky-high prices.

 

[grain elevator]

Proprietary test software. The digital camera already has the sensor, so very easy for test software to monitor when a single pixel sees and does not see light.

As modern cameras are microprocessor controlled, running on a very accurate clock, they can test themselves.

The only simple way that I can think of is a row of LEDs. Each one lights for 1/30s before extinguishing and the next in series turns on.
At a shutter speed of 1/30s, one should see 1 or 2 LEDs lit. Any more and the shutter would be slower than 1/30s.
Next run the LEDs at 1/60s. Again at a shutter speed of 1/60s one should see 1 or 2 LEDs lit.
This can be continued through all the shutter speeds.

Very easy to make, probably £5 in parts or just bits from the scrap-box.

If anyone has any better ideas, I'm happy to have a go at building it.

Some light reading on the subject.

The Way to Modern Shutter Speed Measurement Methods: A Historical Overview - PMC

Exposure time is a fundamental parameter for the photographer when the photo is composed, and the exact length of the exposure may be an essential determinant of performance in certain camera-based applications, e.g., optical camera communication ...

www.ncbi.nlm.nih.gov

I think testing a digital camera shutter is mist easily done taking photographs of an evenly lit surface. You can see tapering as a gradient and test speed via reciprocity. Microprocessor timed low speeds probably won't be off. So just compare high speeds to the slow speeds with a wider aperture or compensated light source.

 

[Chan Tran]

I think testing a digital camera shutter is mist easily done taking photographs of an evenly lit surface. You can see tapering as a gradient and test speed via reciprocity. Microprocessor timed low speeds probably won't be off. So just compare high speeds to the slow speeds with a wider aperture or compensated light source.

Doing so you rely on the fact that the sensor responses linearly to exposure duration.

 

[ic-racer]

But then the shutter is going away in digital camera so it may not be relevant much longer. I wonder now if we can get our hands on those Kyoritsu shutter testers as repair shops for film cameras close down.

Did any one here get this one? I checked and this listing is gone now. I think you can still order a new one from C.R.I.S. but it might be around $5,000.

 

[Alan Edward Klein]

If you're just going to buy a motor and attach a cardboard disk, then you somehow need to know ( accurately ) how fast that's spinning. With a record player, at least it's designed to be pretty accurate. How would you measure the rpm of your motor & disk ?

You got me thinking now, though how to use my digital camera and my turntable, set to 45rpm , to test a new LF lens shutter.

The speed of motors operates off the 50 HZ or 60HZ power input from the electric utility. It's fairly accurate but I'm not sure how much. Maybe others here know?.

 

[Chan Tran]

The speed of motors operates off the 50 HZ or 60HZ power input from the electric utility. It's fairly accurate but I'm not sure how much. Maybe others here know?.

For the kind of turntables that use the synchrous motor I found that the average overtime of the power frequency is very good. Good enough for the clock. Stability I don't think it varies more than 1Hz out of 60 per second. So as far as the speed then it's accurate enough for the shutter as shutter speeds aren't all that accurate. The main problem is that at 45rpm and even at 1/500 the arc is only 0.5 degrees.
I did test with spinning disk running at 1800RPM and 3600RPM I have a larger arc but it's difficult to get good contrast to make measurement.

 

[Niglyn]

I have build a little strobing array of LEDs which when photographed (by a digital camera) or looked at though the film gate of a film camera, will show a number of LED rows. The strobe speed can be set to standard camera shutter speeds, so when viewed, two rows of LEDs should be seen.

If three or more rows are seen, then the shutter is slow.

Only uses a few cheap parts & is easy to build. I have started a new thread for this.

Build a Optical Shutter Tester Cheap, Easy & it Works

Hi, Discussions in a few different treads about methods to measure shutter speed. The best solution is a proper tester (see my other thread 'Build a shutter tester for Focal Plane shutters - Cheap, Easy & it Works) However, over the years all sorts of weird & wonderful ideas have cropped up...

www.photrio.com

billbill100 - Overview

billbill100 has 8 repositories available. Follow their code on GitHub.

github.com

 

[ic-racer]

I can think of a lot of places this would come in handy.

 

[Niglyn]

I can think of a lot of places this would come in handy.

Please list them, as I can't think of any )

An LED ring is also available, 60 LEDS, so would also show angular movement. Shame they cannot be found in 62 or 128 LEDs.
The 60 ring is £10, so can't see many people bothering to make an angular-optical shutter tester.

Would be easy enough to swing a row of LEDs round on a stepper motor, LEDs could also be set to strobe, but again I can't see too many people wanting to build such a device.