Lens Mount Conversions

The Arri PL, Mitchell BNCR and Panavision lens mounts have evolved to support large heavy zoom lenses. They do not lend themselves well to accepting other lenses. There are no unmodified 35mm still lenses that will fit these mounts that I know of. For the 16 mm C mount camera there are adapters for most still lenses and some movie lenses. For the Arri PL and BNCR mount there are some fine adapters made by Arri and Optex for Arri straight and bayonet mount lenses. Homemade adapters with set screws, allow the older Arri straight mount lenses to be extended for close up work.

CAUTION....Arri lenses in BNCR adapters may hit the reflex mirror of a Mitchell BNCR camera (XR-35 or Fries). ALSO BNCR mounted lenses (Baltars and Kowas) may not fit a BNCR mount converted Arri III or IIC. Most 35 mm zoom lenses have enough back focus clearance to be interchanged without problems.

The Fries Mitchell conversions do allow the use of many different mounts on one camera. A Nikon mount can be put on an Arri II C (permanent) and ones are made for the Arri III that are removable made by Nikon and the Becks. This last conversion is not without risk, because the mounts are shimmed and exchanging mounts is an excting operation. If you do a lot of close up work you might consider one of these options. There are a lot of very good close-up lenses available for the Nikon F mount. Canon also makes a fine line of still lenses with an even better mount, but the Canon camera bodies are even shallower than Nikon and not much is possible with an unmodified Canon lens. Canon did make an adapter that will allow Nikkor lenses to be used on a Canon mount camera. It is not very strong. When changing a Nikon mount on an ARRI III be careful about screw length. If too long they can hit the shutter, a very expensive mistake.

One of the earliest mount conversions was the CM-3 Eclair which accepts Nikon Mounts and others quite easily. Don't knock this camera. Carroll Ballard has shot most of his epics with these cameras and Nikkor lenses. They register quite well but don't have much available for motors. Non reflexed Mitchell turrets can be modified to accept almost any mount easily if you can live with a rack-over camera. The turret of the Mitchell can provide a rising or falling front effect with still lenses having enough coverage. Just raise the turret out of the detent. You might not see in the view finder all the image that the film sees because light rays to the ground glass are at an extreme angle. If the lens is raised, the top of the image may seem dark. As the turret is rotated, the lens also starts to shift sideways, but most still lenses have lots of coverage. If you rack the camera over so the aperture is clear, you can see with a mirror if the image is covering the whole frame that might not show in the viewfinder.

If you have an old Arri II C( IIA or IIB), a Nikon conversion has quite a few advantages. You can still use your old straight mount Arri lenses with an adapter and use all the Nikon mount still lenses out there. The price of used Nikon F mount lenses was much less than Movie lenses but climbing because they are getting scarce. The down side is the Nikkor lenses focus backward to most movie lenses, the mounts are not very strong and the lenses focus quite fast (a small rotation gives large focus difference). Don't try to hang big zooms or telephotos on a Nikon mount. A big advantage is the ability to use tilting front and shift lenses on this mount.

Lens Mounts And Adapters For Motion Picture Cameras

Arri Straight
Arri Bayonette
Arri PL
16 mm "C"
Century Optics

The strongest / excellent seating
Very strong / excellent seating
Weak / sloppy seating
Stronger / Very good seating
Very strong / Excellent seating
Strong / Very good seating
Adaptable to many
Strong for size / very good seating
Strong very / good seating

Few adapters will support heavy lenses; zooms and telephotos. Telephoto lenses will tolerate sloppy seating in the lens mount, but wide angle and zooms need very good seating. Lens supports on zooms and telephotos insure good seating and protect the mount from damage because of lens weight and possible strain.

The Adapters





Mitchell BNCR

Arri Straight

Okay for light lenses. Focus wing problems. Not all lenses clear mirror shutter.


Mitchell BNCR

Arri Bayonette

Stronger than above. Focus wing problems.


Mitchell Rack- Over Turret will convert to almost any MP lens mount.

"Hard Front" Arri II's Many Lenses for BNCR won't fit Arri II BNCR Mt. Cameras

Arri PL

Arri Straight

Okay for light lenses.


Arri IIC/B/A / Nikon Mt.


Okay for light lenses. Focus backwards.

Not needed

Nikon Mt.Arri IIC/B/A

Arri Straight

Set screws damage lens. Weak. Remove exposure ears.


Arri III / Nikon Mt.


Okay for light lenses. Focus backwards. Remove exposure ears.

Not needed

Eclair CM3

Arri Straight

Okay for light lenses. Weak.


16 mm "C" Mt.

Arri Straight

Okay for light lenses. 16mm lenses will not cover 35mm film.

Birns &Sawyer

16 mm "C" Mt.

Canon/Nikon/Other Still

Okay but lenses not designed for smaller format. Image suffers.

© Copyright 1999-2004 Ron Dexter. All Rights Reserved.