Berlin and Moscow – Optics and Cameras – Part II

Starting at the point where I wrote this :

“FTF or Register is the distance between/from flange to film, or mount to film, and thus also flange/mount to sensor.
This distance ensures that the focus of the lens falls on the right place.
Otherwise told, you can assume that a lens is made compatible to a certain mount.”

Now you know that a camera has an FTF or Register.
But, also the lens has a Register – and this is very important.
Lets take a look at the Industar-50, f3.5 50mm lens.
It’s a collapsible lens with M39 LTM mount ( LTM = True Leica Thread-Mount ),
mostly used on rangefinder cameras like Zorki, Fed … and Leica.
Rangefinder -> that means that the lens is closer to the film than with a SLR type of camera.
The Register of these type/brand rangefinders have a Register of 28,8mm
I wrote especially M39 LTM, because there are other kind of M39 mounts.
M39 LTM has 26 turns-per-inch or threads-per-inch (tpi) or approximately 0.977 pitch,
Canon also has used M39, but this one had 24 tpi thread mount, and was called “J-mount”.
This is the first incompatibility issue.
But there’s also another issue,
Zenit also used this mount, M39 LTM, for its earlier SLR cameras.
But an SLR has a bigger Register due to its internal mirror, like all SLRs.
These Zenit SLRs have a Register of 45,46mm
So, this Zenit uses lenses with a bigger Register, but with the same mount !
That is the second incompatibility issue.
The same “mount” incompatibilities like the M39 with different thread pitch,
is also found in other mounts like the M42 or bajonet types.

let’s summarize:

(D)SLR’s have a bigger Register than system cameras, mirrorless or rangefinders,
due to that bigger Register, system cameras, mirrorless and rangefinders
are more easily adaptable to lenses than (D)SLR’s – you just need a good mount adapter.

Lenses made for system cameras, mirrorless and rangefinders, are almost impossible to use on (D)SLR’s
unless you would make use of an adapter with a lens compensation ( adapter with build in lens )
but that would undo the advantages of using a vintage or different brand lens.

If you are interested in vintage lenses, M39 Leica mount, M42 or other …
and you need to buy a (new) camera,
system cameras, mirrorless and rangefinders are more favourable above (D)SLR’s.
That being said, Nikon (D)SLR’s are the worst because of their 46,5mm Register
( one millimeter bigger than M42 lens Register )
unless you are not interested in focusing to infinity.

Also, look up it’s Register in Google, if you want to purchase a lens that you are not familiar with,
or look up the kind of camera it was intended for.
Like : an M39 lens for Leica LTM, Zorki and FED is NOT the same as an M39 lens
made for Zenit SLR – although the mount and thread fits.

There are many sites having a list of camera/lens FTF or Register lists.
Here’s one I found:

Adapter Calculation:
A Samsung NX camera has a register of 25,50 mm,
to mount this Meyer Optik Görlitz Primagon 1: 4.5 / 35mm M42 lens,
you need an adapter that is :
(M42 register = 45,46 mm)
45,46 – 25,50 = 19,96 mm

Samsung NX with vintage M42

Samsung NX with vintage M42

Samsung NX with vintage M42

Adapter Calculation:
Here you can see the difference,
the Meyer Görlitz Primagon was made for SLR,
so it has a large Register ( 45,46 mm )
This collapsible Industar 50 – 50mm f3.5 M39, was made for rangefinder,
the Register is thereby much smaller : 28,8 mm.
So in this case, you need following adapter :
(lens) 28,8 – 25,50 (NX) = 3,3 mm

Samsung NX with Industar 50 "Red P"  50mm f3.5

Samsung NX with Industar 50 "Red P"  50mm f3.5

Samsung NX with Industar 50 "Red P"  50mm f3.5





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