An Adapter's Guide to Camera Mount Register Distance

That's the one I usually use, but there are others....

http://www.markerink.org/WJM/HTML/mounts.htm

http://camera-wiki.org/wiki/Lens_mounts

https://en.m.wikipedia.org/wiki/Flange_focal_distance

There are some mounts not listed in other lists, and some mounts have different values listed, so you have to use caution when using these values.

To explain the use of these, pick a lens mount(EF), all the camera mounts with a larger measurement will be impossible to mount that lens to and still reach infinity(modification or optics will be required), of the mounts that are shorter, a simple adapter is required that bridges the gap between the cameras register and that of the lenses, for example, a Canon EF lens(44mm) and a Sony E mount camera(18mm)

44-18=26mm thick adapter, well that's a theoretical number, in reality it will likely be just a fraction smaller so you can still reach infinity, as everything has a tolerance, or an amount of variation.

Tom Caldwell wrote:

Some extra crumbs of information:

The Samsung NX mount is one of the longer Mirrorless mounts as a result it only adapts to LTM (M39) with difficulty and, to my knowledge, LM requires permanent mount surgery(replacement).

NX is nearly the same registration as Leica M & LTM, but the mount does not have a large enough diameter to accommodate the M mount, there is just enough room for LTM.

This was one reason NX isn't as popular as other mirrorless cameras.

Focal reducers require space between Lens and camera to fit their operating elements. What is not often understood is that the process of focal reduction shortens the required adapter length. Provided that it can be done, the shorter length of the adapters can be visually pleasing.

Focal reduction can give more light gathering ability (one stop for 0.71x) and improve lens performance (compression of image). Older focal reduction adapters seemed also to make lens faults more obvious. But Brian C stated that his design for the Metabones Ultra for M4/3 mount actually enhanced the performance of any lens mounted by it. I have no reason to doubt his claims.

Rangefinder lenses have a short flange focal length - too short to make a focal reduction adapter practical. Several (quite a few) RF lenses have a rear protrusion which makes it impossible to fit them inside many mirrorless mounts as they can hit up against internal baffles, electronic contacts, or even the sensor.

I don't know of many that touch the sensor, maybe a few WA/UWA lenses that get very close to the film might be in danger to the shutter and a remote possibility that the sensor could be touched.

Lens throat diameter has a bearing. If the host camera mount is wide enough then a small mount lens can be recessed into the adapter where the FFL (register) is shorter than the camera mount. eg: C to M4/3.

There are practical difficulties.

A very wide MF lens may have its focus/aperture rings difficult to access. Canon EF lenses can provide AF services via electronic adapters but there are so many of them (lenses) that the performance is variable across both lenses and differen brands of adapter.

Canon EF adapters in their more recent iterations seem to be coming of age and are more truly useful for quick accurate AF over a wide range of both Canon and other brand lenses in EF mount.

The body helps, the faster the camera handles the processing of the focus data, the faster the lens can be moved.

And of course if an adapter is badly made then there might be problems in focusing lenses to infinity. But don't always blame the adapter as the lens itself might be at fault.

very true, always compare multiple lenses to confirm an adapter is causing issues.

-- hide signature --

Tom Caldwell

Stephen H. Westin wrote:

Alas, the Cornell address has gone dark. My lens register lists are now available at

http://stephen-westin.com/misc/mounts-alphabetical.html

and

http://stephen-westin.com/misc/mounts-alphabetical.html

I assume you meant this link: http://stephen-westin.com/misc/mounts-by-register.html

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-Stephen H. Westin

Thank you Stephen, very much appreciated, and I speak for a number of adapted lens users, it has been a very handy list to use for reference, especially the more uncommon lens mounts that don't have readily available adapters, so I'm very happy to see its return, I've had to use the Internet Archive since the original site started to return 404's.

Stephen H. Westin wrote:

mapgraphs wrote:

If you've been adapting, you probably already know about Stephen Westin's site listing register distances for most mounts. If not, here's the link. It's pretty much self explanatory:

http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

That page has been superseded by https://stephen-westin.com/misc/mounts-by-register.html ; I haven't worked at Cornell for over 15 years, but I don't have any way to replace that page to redirect it.

– Stephen H. Westin

I was going through my bookmarks in preparation for DPR's demise.  I thought I would  mention that Stephen Westin's website is no longer there due to his passing .  The Cornell listing however is still there, but not current.