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Leica curious
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PostPosted: Fri May 11, 2007 8:29 pm    Post subject: Leica curious Reply with quote
What is the deal with these "cams" on leica lenses?


PostPosted: Fri May 11, 2007 8:49 pm    Post subject: Reply with quote
I am not sure of what technically is a "cam", but it is related to the mount. Different Leica reflex cameras have different cam compatibility. Some cameras can only mount lenses with one cam, some can mount only those with one or two cams, some can mount the lenses with one, two or three cams, and finally, the latest models have the "rom", which has something to do with automation.


PostPosted: Fri May 11, 2007 9:01 pm    Post subject: Reply with quote
Is there a different adapter for each of these to go onto EOS?


PostPosted: Fri May 11, 2007 9:10 pm    Post subject: Reply with quote
No, cams are absolutely irrelevant for EOS use and any adapter will do.


PostPosted: Fri May 11, 2007 9:56 pm    Post subject: Re: Leica curious Reply with quote
hacksawbob wrote:
What is the deal with these "cams" on leica lenses?


I'll have a go at explaining:

With rangefinder cameras, where the viewfinder is separate to the taking lens, there is a slight parallax between the two lenses. The amount of this parallax difference changes when the taking lens is focussed on distant and close objects. The picture frame in the Leica viewfinder is adjustable to take account of this parallax so that the picture you see in the viewfinder frame is more or less identical to the picture seen by the taking lens. The function of the cam is to tell the VF frame where the taking lens is focussed.


PostPosted: Fri May 11, 2007 9:57 pm    Post subject: Reply with quote
Peter, these are reflex camera lenses.


PostPosted: Fri May 11, 2007 10:05 pm    Post subject: Reply with quote
Orio wrote:
Peter, these are reflex camera lenses.


Ah! With reflex cameras the cams are used for metering. The function is the same - to pass on the focussing distance.

http://tinyurl.com/28v6dx


PostPosted: Sat May 12, 2007 12:17 am    Post subject: Reply with quote
reflex? paralax? you've lost me I'm affraid Embarassed


PostPosted: Sat May 12, 2007 12:58 am    Post subject: Reply with quote
Orio wrote:
No, cams are absolutely irrelevant for EOS use and any adapter will do.


Excuse me, is my nose in the way?

"Cams" is a diminuitive of "camels" and when talking of different mounts
and such, you first have to recognize bactrian, from dromedary.

Don't thank me, glad to help, have a nice evening... Wink

Now back to your regularly programmed discussion, interesting stuff!

Bill


PostPosted: Sat May 12, 2007 2:12 am    Post subject: Reply with quote
I've never had a Leicaflex but I believe the cams are to tell the meter what aperture the lens is set at. The original Leicaflex didn't meter through the lens, so the meter just had to know the selected aperture. In later models with TTL metering, the meter has to know both the selected aperture and the maximum aperture of the lens (since that determines how much light is reaching the TTL meter). With an adapter on a DSLR, you're metering stopped down so none of it matters.

A bit of speculation but I think it's pretty close. The difference is essentially the same as the difference between Non-AI and AI Nikkors, which went through the same transition.


PostPosted: Sat May 12, 2007 7:43 am    Post subject: Reply with quote
hacksawbob wrote:
reflex? paralax? you've lost me I'm affraid Embarassed


"Reflex" literally means the camera uses a mirror to reflect the image onto the viewfinder screen. There are single lens reflex (SLR) and twin lens reflex (TLR) types. The twin has one lens for taking the picture and the other for viewing the image and usually the two lenses are linked together by cogs so they both have the same focussing distance. A SLR views the image through the same lens that the film or sensor sees through, so the mirror has to flip up out of the way when the shutter fires. The standard 35mm SLR camera only became the normal consumer camera in the 1960's. Before that the typical consumer camera was either a rangefinder or a cheapo fixed lens camera, and before that it was a folding camera with bellows or a box camera, both with tiny little prism viewfinders that reversed the image.

Parallax - hold up a finger at arms length and look at it through one eye and then register your attention on the object immediately behind your finger - ideally this should be at least 5 metres away. Now change eyes and look where your finger has moved to in relation to the same object. The difference between the two images is called Parallax. This affects any camera that has separate viewfinder and taking lenses. Cheap cameras don't usually bother, but Leicas and Contax G rangefinders (probably many others too) have the facility of adjusting the picture frame lines in the VF to show exactly what the taking lens is seeing - the frame moves as you turn the focus ring on the taking lens. This is the function of the cam.


PostPosted: Mon May 14, 2007 12:52 pm    Post subject: Reply with quote
Right thanks for that I understand know.


PostPosted: Thu May 17, 2007 8:00 am    Post subject: Reply with quote
Click here to see on Ebay how about these with the spectacles, any good for EOS mounting?


PostPosted: Thu May 17, 2007 8:03 am    Post subject: Reply with quote
hacksawbob wrote:
Click here to see on Ebay how about these with the spectacles, any good for EOS mounting?


Nope, these are for Leica rangefinder, incompatible register distance.


PostPosted: Thu May 17, 2007 8:19 am    Post subject: Reply with quote
Orio wrote:
hacksawbob wrote:
Click here to see on Ebay how about these with the spectacles, any good for EOS mounting?


Nope, these are for Leica rangefinder, incompatible register distance.


That's true!
This is a shame, since it is just fascinating to use those. I had the chance to play around with such a thing at the last fair. Amazing!
(Maybe they work properly at the M8...)


PostPosted: Thu May 17, 2007 2:08 pm    Post subject: Reply with quote
Click here to see on Ebay please tell me this wont fit on my camera too!


PostPosted: Thu May 17, 2007 2:15 pm    Post subject: Reply with quote
I'm afraid I have to tell you that this is one of the best tele lenses ever built.
And I'm pretty sure that you can adapt it to your cam... Twisted Evil Wink


PostPosted: Thu May 17, 2007 2:29 pm    Post subject: Reply with quote
How much are you prepared to spend, Bob? Because unless a miracle happens, you are not going to take this babe home for less than 3,000 Euros. Shocked


PostPosted: Thu May 17, 2007 3:02 pm    Post subject: Reply with quote
exactly, that is why I wanted you to tell me I couldn't use it!


PostPosted: Thu May 17, 2007 3:28 pm    Post subject: Reply with quote
hacksawbob wrote:
exactly, that is why I wanted you to tell me I couldn't use it!


OK, you can't use it Wink
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