Converting a Bolex H16M to Ultra-16, part 1

For some years now I’ve owned a little-used Bolex H16M camera, and had a yearning to modify it to Ultra-16.  Whenever I attempt something like this,  I first satisfy myself that the camera’s  registration is rock-steady. See  https://filmisfine.com/blog/how-steady-is-your-movie-camera/

Having no turret like most Bolex’s,  it’s quite easy to get started on the job.  It goes something like this….

Remove the leather and nameplate to expose the lens mounting plate.   Put the camera out of springwound mode and ready for backwinding.  Use the backwind key to take the shutter away from the gate area.   Remove the 4 big outer screws and gently ease off the lensmount.  Unlike the more complicated Bolex models, there’s no problem upsetting the timing.

Inside the camera remove the back pressure pad.   Unscrew the gate mounting-plate,  but as a guide for replacement its a good idea I think to firstly mark around the edges with a scriber.  Now remove the 4 small screws that hold the gate, and slide it out gently from between the side leaf springs.  It goes without saying that the gate must not be scratched at all.  Don’t  remove the top and bottom bolts.

The gate needs to be enlarged sideways to bring it out to 1.85:1  ratio.  The area between the perfs (by the frame-line) that is seen in Regular-16,  won’t be visible.  Although of course the image carries on being formed in this area,  so it is possible to use the camera normally as well.  1.85:1  is the same ratio as 35mm widescreen, if you are thinking of blowing up to 35.  With my modification I decided to go wider than 1.85:1,  something approaching  2.2:1.  However, I knew I would run into problems with the latent edge markings appearing within the image area,  unless I could find film-stock without these markings.   1.85:1  though has no such problem.  I was also a little concerned that the wide gate might not support the film sufficiently and cause unsteadiness or lack of flatness.  But happily this hasn’t happened.  The final width is 13.3mm,  leaving only 2.7mm to support the film.

Now for the widening !  I used a chunk of wood that I’d  used on another U.16 job,  attaching the gate firmly with drawing pins cushioned with cardboard.   Over the top I mounted a magnifying glass,  and started filing away with a needle-file.   Lots of breaks is a good idea with this kind of intricate work.  You don’t want to jab the gate by mistake.  Later on I changed position and filed from below, see photo.  I also paid particular attention to the top and bottom edges to make a smooth bevel,  and rounded off the corner bits where the film would touch.  Afterthought:  it may have been safer to completely cover the gate moreorless with card, as surgeons paper over patients !  Finally, I  wrapped fine emery cloth around the file and worked with this.  Then to finish off, the finest emery grade.

I now placed the enlarged gate into the mounting-plate again and loosely put it in position.  Obviously it was also necessary to remove some metal from the front plate,  so I first scribed marks either side and then filed away.  This is quite hard steel.  After finishing with emery I cleaned everything thoroughly,  then painted all the filed parts including the gate edges,  matt black.  When satisfied all was OK,  I reassembled the gate into the camera,  in precisely the same position and making sure that none of the 4 screws protruded.   With the camera laying on its back,  I then eased the lens plate back into position,  making sure the claw was out of the way,  and then turned the backwind key.  All looked fine and so I replaced the 4 big screws,  tightening them diagonally. Then stuck on the leather.

Next I loaded some dummy film and ran the camera.  The movement looked fine to the eye.  How it really performed would be tested later.  When the gate was taken off black paint came off also,  so I touched up all this again so that the important light seal would remain.  This is how the gate and front plate looks now, with some film loaded.                                       to be continued….

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