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Dead stop

dudler

Time for an update: I still use film, though. Not vast quantities, but I have a darkroom, and I'm not afraid to use it.

I enjoy every image I take: I hope you'll enjoy looking at them.
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Dead stop

29 Apr 2021 8:18AM   Views : 174 Unique : 111

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Let me introduce you to a little device you donít see a lot these days: itís called a focus infinity lock. Iíve met it on Leica lenses dating back to the Thirties, and on Fifties/Sixties Canon rangefinder lenses. Itís very much a rangefinder thing.

Very simple: thereís a lug on the focus ring of the lens, typically at around 7 oíclock 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, itís easy to reach with your left forefinger.

It has two purposes: the little knob on the front is spring-loaded forwards, and when itís 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.

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Thatís handy for landscapes, as a quick reaction to seeing a shot doesnít 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.

Iím not aware of any modern lens fitted with this device, though some smaller Leica lenses have a lug to make focus easier Ė it just doesnít 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 Ė the mechanism hasnít seized up!

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Comments


dudler Plus
17 1.6k 1840 England
29 Apr 2021 8:19AM
The lens in these pictures is a Canon 28mm f/2.8, mounted on a Leica M-6.
BobinAus Plus
5 3 10 Australia
29 Apr 2021 11:28AM
Hello John, the Pentax DA*11-18 F2.8 zoom lens (an APSC lens released a couple of years ago) has a sliding switch that can lock the focus at any distance. I understand that its primary purpose is to lock focus at infinity before night-sky photography but of course it could be used more generally. Bob
dudler Plus
17 1.6k 1840 England
29 Apr 2021 10:00PM
Bob, that's a good idea, and a slightly different thing, because it doesn't give a preset and fixed infinity focus: I'm guessing that you have to set it in daylight, as the lens most likely goes past infinity as all the AF lenses I can think of do.

I think that Samyang have fitted something similar to a new wideangle lens, citing astrophotography as the application.
BobinAus Plus
5 3 10 Australia
1 May 2021 7:12AM

Quote:Bob, that's a good idea, and a slightly different thing, because it doesn't give a preset and fixed infinity focus: I'm guessing that you have to set it in daylight, as the lens most likely goes past infinity as all the AF lenses I can think of do.

I think that Samyang have fitted something similar to a new wideangle lens, citing astrophotography as the application.



As you guessed, John, the lens has to be focused and locked in daylight. In the little night-sky photography that I've done since acquiring the lens, I've found the lock to be very handy. It's more convenient and effective than masking tape (or the like) in preventing me from unintentionally altering the focus as I bumble around in the dark. However, one must remember to unlock the focus before 'normal' photography the next morning! As I've discovered, that step is easily forgotten Blush after being 'out in the field' until well after midnight: Another plus for checklists (hard copy or mental) instead of a camera's user mode settings IMHO. Bob
dudler Plus
17 1.6k 1840 England
1 May 2021 10:14AM
I had a boss who talked about 'brain-on' activity... His view, I think, was that a lot of people go about their lives in 'program mode' and don't ever think about what they're doing...

Photography, to be satisfying and productive, needs a good bit of switching on of the little grey cells.

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