These days, with the digital technology we have available, measuring time is a fairly simple affair. Even for most of us at home, we can get a suitably fast (and very cheap) microcontroller like an Arduino or ESP32 and measure times down to tens of thousandths of a second. But how did they do it 100 years ago, when nothing was digital, but where accurately measuring time was vital for camera operation?
Well, in this video from SmarterEveryDay, we find out as Destin takes a trip to Finland to visit the Kamera Store. Kamera Store is a company that restores and revives camera gear. They cover everything from the newest mirrorless cameras to absolutely ancient relics from photography’s past. But how they test those shutter speeds on older mechanical cameras involves some absolutely fascinating principles.
Using analogue equipment to measure times as fast as even 1/1000th of a second – which is pretty tame by today’s standards where electronic shutter speeds can go up to 1/32,000th of a second even in consumer cameras – involves some pretty fancy tech for its day. For most of us growing the 80s before CDs took over, the principles involved in the machine used to test fast shutter speeds are something that many of us would be familiar with from record players.
The way the principle is applied in this particular machine for measuring shutter speeds actually exploits what is generally regarded today a downfall of most CMOS sensors. Rolling shutter. This is the process whereby a scene is scanned on the sensor line-by-line in order to create the final image. It’s the phenomenon that creates bendy (or completely disconnected) propellers and does weird stuff to guitar strings.
Essentially, this device creates a rolling shutter effect that you can see with your eyes, thanks to persistence of vision. It allows you to see a pattern through the camera’s shutter and depending on how the lines line up with the reference images in the service manual for that particular camera, you can tell whether a given shutter speed is firing too fast or too slow.
It’s a fascinating application of the principle. It’s an application that probably wouldn’t occur to many people today. The fact that these machines were around a hundred years ago really shows off the ingenuity of camera techs back then to not only be able to create cameras with such shutter speeds but to design and build the gear to test they were actually hitting those speeds accurately.