Dead stop

Dead stop

Let me introduce you to a little device you don’t see a lot these days: it’s called a focus infinity lock. I’ve met it on Leica lenses dating back to the Thirties, and on Fifties/Sixties Canon rangefinder lenses. It’s very much a rangefinder thing.

Very simple: there’s a lug on the focus ring of the lens, typically at around 7 o’clock as you look at the lens from the front. If you hold the camera with your right hand to operate the lever wind and shutter release, and support the camera with your left hand, it’s easy to reach with your left forefinger.

It has two purposes: the little knob on the front is spring-loaded forwards, and when it’s released, and the lens is set to infinity it locks in the little cut-out you can see in the last picture. Bevelling of the mechanism means it snicks into place without pressure on the button as the lens is focussed to infinity, and it keeps the focus set there until pressed towards the back of the camera.



That’s handy for landscapes, as a quick reaction to seeing a shot doesn’t necessarily take in the rangefinder spot (and, indeed, earlier Leicas had the rangefinder in a separate window from the viewfinder!) and it also provides a way to focus a very small lens with a very narrow focus ring.

I’m not aware of any modern lens fitted with this device, though some smaller Leica lenses have a lug to make focus easier – it just doesn’t lock. AF lenses, and manual focus lenses made for AF cameras typically focus past infinity to allow for imperfections in engineering, and unusual operating conditions.

So if you come across an older camera with this sort of mechanism on standard or wideangle lenses, press it gently and focus – the mechanism hasn’t seized up!