Measuring Milliseconds Mechanically

When the Leica camera was introduced in 1925, it was an immediate sensation. Using 35 mm movie film, which was abundant and inexpensive, with a horizontal format providing a 24×36 mm image and lenses of impeccable quality, it was small, light, flexible, and with the addition of interchangeable lenses in 1930, usable for a wide variety of photography. In 1935, the Leica IIIa extended the shutter speed range down to 1/1000 second, making the camera ideal for sports and action photography.

But, given the Leica’s reputation for precision, how was the shutter speed to be measured and adjusted accuratelyin an age before high-speed electronics? With another bit of clever engineering, of course!