Movie Cameras, Uncategorized

Converting a Bolex H16M to Ultra-16, part 2

Last time we tackled the gate widening.  Now for the sprockets.  Because the film touches areas beside the sprocket teeth,  it’s necessary to remove any metal that might cause wear of the image.  Normally this wouldn’t perhaps happen but its better to be safe than sorry.  Removal of the two sprocket wheels is simple with a screwdriver.  Firstly though, ink a mark on the wheel next to a convenient point on the camera. Note there is an angled slot at the edge of each wheel that when lined up will clear the loop-former,  so turn the camera with the backwind key to get it in the right position.  Once removed, carefully grip each sprocket wheel in a vice.  In the photo you can see how much I filed off at each tooth.  It’s brass so quite easy.  Leave some metal at the base of each tooth and don’t damage the tooth itself. Finish off with fine emery wrapped around the needle-file.  Take your time !  Now turn your attention to the other side.  There are two ridges that normally support the film. Important:  don’t  touch the outer one.  The inner ridge needs to be removed.  This can be done with a lathe, or it’s not a long job to simply file it off.  As long as it doesn’t  touch your precious image there’s no problem.  So now you have sprockets that won’t harm the Ultra-16 image in any way.

Replace the sprockets,  ensuring that they are lined up accurately within their guides.  And also line up the ink marks as before.  Don’t tighten the screws properly yet.  Place some film in the threading path through the gate so that the claw engages it,  and close the loop-formers.  If necessary,  turn the sprockets slightly so that the film hugs the top and bottom loop-former.  By trial and error you’ll find the correct position for the sprockets,  and now fully tighten their grub-screws.  With loop-formers still closed, check the movement by winding the film by hand,  and finally by running the camera normally. Also check that the auto-threading feature works OK.  Now release the loop-formers and run the film at fast speeds to see that all is well.  Pristine unused film is best so that you can determine whether or not any damage occurs.  If it does,  it’s a simple matter to find the cause,  ink-marking the stationary film at various places along its path before you withdraw it from the camera.  An old projector lens is ideal as a magnifier.  Examine each perforation and its environs very carefully.

Next time we’ll look at the viewfinder mod.  Currently I’m  still tackling this !

to be continued…..

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  1. Greetings from Connecticut, USA:

    Discovered your FilmisFine Website, while searching for information on conversion of a late ’50’s H16-Non-Reflex camera to Ultra16.

    Any news of your progress on conversion of the camera’s viewfinder to Ultra16 would be helpful.

    Is it the Octometer viewfinder that you are working on, or the critcal-focus prism, or both?

    Thank you for this interesting article, as well as other items in the various departments of your site.

    Best wishes,


    1. Hello James, I’m afraid other projects have got in the way a bit, and I still haven’t converted the viewfinder ! It’s the Octameter one on the side door. I’ve been using it as it is without the proper masking and sofar so good, though obviously not very good for precise framing of shots. I’ll hopefully get this done asap. But my excuse at the moment is that there’s a film in the camera! and I need to have access to the gate image (with some tracing paper perhaps) to compare it with the Octameter image. The H16M I have doesn’t have a critical-focus prism. However, I’ve been very happy with the U16 results sofar. All best with your mod, and do let us know how you get on.

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