What is an "infinity lock"?

[Jamie Pillers]

I often see discussions of older RF lenses include the term "infinity lock". What is that?

 

[gdi]

It locks focus at infinity, to unlock it you have to push a button when focusing closer.
Under the thumb in this photo...

http://farm4.static.flickr.com/3179/2484554369_1a6cca00bb.jpg?v=0

 

[Andrew Sowerby]

Does just like it says on the tin ... but why? What's the point?

 

[Sonnar Brian]

It helps unscrew the lens on a Leica and dismount them on a Contax/Nikon, otherwise undo force is placed on the helical. On the Nikon and Contax, the infinity lock is built into the camera.

 

[Jamie Pillers]

Thanks everyone... I get it now.

 

[Andrew Sowerby]

Thanks, Brian. I've always wondered about that.

 

[BillP]

It helps unscrew the lens on a Leica and dismount them on a Contax/Nikon, otherwise undo force is placed on the helical. On the Nikon and Contax, the infinity lock is built into the camera.

In use, it has a couple of other benefits. The lock becomes a focussing tab - useful on the smaller lenses. The tab also enables you to work out where the lens is focussed by feel - not as silly as it sounds. I can prefocus my IID and 5cm Elmar by feel before raising the camera to my eye as a result.

Regards,

Bill

 

[pfoto]

The first version Summicron 35mm/f2 lenses built in Germany also had an infinity lock that is cleverly hidden in the focusing tab.

 

[ferider]

As Bill and Brian said.

Nice new avatar, Jamie

PS: an example on one of my favorite lenses; the handle a little right of the center of the pic.

 

[Pherdinand]

An infinity lock?
An infinity lock is just another failure of industrial design.