Monday, 19 April 2010

Register distance

The register distance, also referred to as the flange focal distance, is the distance between the lens mount, and the film plane. Modern cameras don't use film anymore, so the film plane is in fact the sensor plane.

SLR cameras, with a moving reflex mirror behind the lens mount, need a fairly long register distance. The reason why Micro Four Thirds cameras can be made more compact than SLR cameras, is that they don't need the reflex mirror, and can have a shorter register distance.

A lens mount with a short register distance can be considered a universal mount, since it is possible to create adapters for mounts with longer distance. Micro Four Thirds is such a mount. There are adapters for a number of different formats, e.g., Nikon F and Pentax K.

For comparison, here is the register distance of various formats:

Samsung NX MiniVery short
Pentax Q9.20mm
Nikon 117.00mm
C mount17.526mm
Fujifilm X17.70mm
Sony E (NEX)18.00mm
Sony FZ19.00mm
Leica L (T and SL)19.00mm
Micro Four Thirds19.25mm
Hasselblad XCD20.00mm
Samsung NX25.50mm
Fujifilm G26.70mm
Leica M27.80mm
Konica Hexar RF28.00mm
Olympus Pen F28.95mm
Contax G29.00mm
Contax RF34.85mm
Four Thirds38.67mm
Konica AR40.70mm
Canon FD42.00mm
Minolta MD43.72mm
Sigma SA44.00mm
Canon EF44.00mm
Minolta AF/Sony Alpha44.00mm
Pentax K45.46mm
M42 screw45.46mm
Contax/Yashica45.50mm
Olympus OM46.00mm
Nikon F46.50mm
Leica R47.00mm
Contax N47.00mm
Arri PL52.00mm
Oct-1961.00mm
Mamiya 64563.30mm
Pentax 64570.87mm
Hasselblad 50074.90mm
Pentax 6x784.95mm


The new Samsung mirrorless NX format has a longer register distance than Micro Four Thirds. However, the Samung format still has a shorter distance than most relevant formats, e.g., Leica M, so that it is possible to create adapters just as easily as for Micro Four Thirds.

On the other hand, the Samsung NX has a register distance about 2mm shorter than Leica M, which may be why Novoflex has not yet announced an adapter for it. 2mm may be too short to make a quality adapter.

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