Canon's detachable head lenses

[nodyad]

Two of my '50's-era Canon long lenses have detachable heads that unthread from the focusing portion of the barrel: the 135mm f/3.5 (chrome) and the 100mm f/3.5 (black and chrome). Other than that the general design is the same, the thread diameters and back focal lengths are different. It's like there is a hint of a reason, but I'm not aware of any common focusing unit or accessory that these heads would be used with (unlike long lenses with extenders clearly intended for use with the reflex finders). Can anyone shed light on why these lens heads are detachable?

The lenses in question:

 

[Sonnar2]

I think this is mainly for production efficiency reasons, although for certain lens heads (i.e. the 100/2) there are also mountings for SLRs (discussed in the Mirror Box thread) which are somewhat scarce. Of course this wasn't an argument when the 100/3.5 was designed, because in 1951 didn't planned to make any SLR cameras.

I found that both parts of my 100/3.5 are marked as "fit together", probably after testing on an optical bench for focussing accuracy, so that they shouldn't be mixed up if someone has more than one lens of this kind.

I found that the lens head of my 85/1.8 is also removable

regards, Frank

 

[CanonRFinder]

Two of my '50's-era Canon long lenses have detachable heads that unthread from the focusing portion of the barrel: the 135mm f/3.5 (chrome) and the 100mm f/3.5 (black and chrome). Other than that the general design is the same, the thread diameters and back focal lengths are different. It's like there is a hint of a reason, but I'm not aware of any common focusing unit or accessory that these heads would be used with (unlike long lenses with extenders clearly intended for use with the reflex finders). Can anyone shed light on why these lens heads are detachable?

The lenses in question:

Hi, Check on this RF link as these lenses were discussed for some period and also I mentioned the serial numbers these lenses fell in and what adapters they needed. Interesting lenses. Peter K

http://www.rangefinderforum.com/forums/showthread.php?t=37369&highlight=mirror+box

 

[nodyad]

Thanks for that link, Peter. I missed it in my search. The information is quite complete, thanks to the many separate bits of information pulled together there. That thread merits being made sticky as a system feature (of sorts) of Canon RF long lenses.

 

[CanonRFinder]

Pleasures mine but you may as well give me the serial # of the lenses and I will add them to my database.

 

[nodyad]

Sent a PM with the info.