INTERMEDIATE GEAR PROBLEMS

All bolex 8mm cameras are spring wound. The torque from the spring motor drives an intermediate gear which in turn drives a vertical shaft that interfaces with the speed regulator and the claw mechanism. If you have a Bolex 8mm camera, there is one of these gears inside your camera. You want to repair the camera? You need to do a few things first or you will have a intermediate gear problem. Here's why...

Unwind Me

The first step to repair any spring wound camera is to 'run the motor down'. This means to press the run button until the camera motor stops turning. Not sure? Button doesn't start the camera?

Older cameras are lubricated with both oil and grease. After 50+ years of storage, the grease can harden. The hardened grease can prevent the motor from working. Solution? Remove and re-lubricate. To do this you need to disassemble the camera. This is where the intermediate gear can get damaged.

If you fail to run the motor down properly, the remaining spring tension will still be applying torque to the drive gears. Not knowing this, you remove the 5 screws holding down the cameras top plate and remove the plate. You see the insides of the camera. The gears, regulator, the spring motor, etc. You think, "All I need to do is to oil or grease them!" 

Well...not quite.

They are still filthy dirty so they should be cleaned. You figure this out too and look over the camera. You find the 4 screws holding down the shutter assembly. You accurately conclude that removing the 4 screws will allow you to remove the shutter assembly and further disassemble the camera. So out comes the screwdriver and you take out the 4 screws.

Pleased that you are saving money by doing it yourself, you carefully pull off the shutter.

Bzzzzzzzzzzz-zap!

You look inside and see all the teeth of the intermediate gear fully stripped off. Oops! The spring motor supplied the torque. The only thing keeping the spring motor's gear from turning was the shutter and you disconnected that when you removed it. The springs motor forced the intermediate gear to turn at "light speed" and during the rapid unwind, the bakelite (plastic) gear teeth grazed another metal gear. This sheared off all those teeth.

You now need another intermediate gear :( You may need another spring motor, too - Whaaaaaa!!!! Spring motors do NOT like to go from wound to unwound in less than a split second. It can damage the internal flat spring when it hits the end stop.

Need replacements parts? Bolexrepair.com has them.

Next time - run the motor down :)

SHUTTER CONTROL AND F/STOPS

Can I Cut The Light With The Shutter Setting?

Bolex D8L shutter settings varies from about 180 degrees (the silver half-moon) to zero degrees (the black half-moon). The half way setting of  90 degrees is accurate enough. So the answer is yes, you can a light cut 1 stop by selecting the mid point shutter setting. Controlling the light with the shutter does works well in still photography as the images are not moving.

If you set the shutter to half-closed (the half black/half silver HALF MOON symbol on the shutter dial), that setting is half way from the maximum open of 180 degrees to fully closed. About  90 degrees. The shutter angle will be cut by 1 stop. See page 47 of the Bolex D8L manual.

See this link for more of how a shutter works:

     http://en.wikipedia.org/wiki/Shutter_%28photography%29

D8L accuracy is not specified, but it should be in "ballpark acceptable". As with all footage shot on a Bolex, keeping records of the setting and the results is a very good idea. Everybody's mileage will vary as the camera settings/projectors/screen combinations will always be different.

Movie Film Camera

Use and effect of the shutter is slightly different with a movie film camera.  There are 3 basic ways to set light with a motion picture camera:

          1) Set the iris for the light - The DOF will be what

          it will be. This is how the Bolex manual explains

          setting the iris for the light.

          2) Set the pre-selected DOF with the iris, and

          control the light with ND filters or more light.

          3) Use both ND filter and iris settings in

          combination.

The method of setting light in professional motion picture film production cameras is primarily through a pre-determined iris setting (f-stop) and then re-adjusted for actual light using neutral density (ND) filters. Typically you will have either too much light or not enough.

With too much light, you can close the iris slightly or add an ND filter. Too little light, open the iris or take out or decrease the ND filter's strength. The situation here is changing the iris will affect the depth of field (DOF). ND filters will not affect the DOF.

How To Set

First, you select the location (indoors or outdoors) and the subject. Say you desire an f~5.6 setting for a slightly blurred background. Using your lightmeter, get the approximate f-stop setting by metering the subject after dialing in the f-stop for f~5.6 on the light meter's dial. Next, add or subtract light, as necessary using ND filter, bounce cards, light fixture, etc, to get the correct amount of light.

More Or Less Light

Outdoor light can be raised with a bounce card, an auxiliary hot light, etc. Outdoor light can be cut with an ND filter and anything that will lessen the light falling on the subject. Indoor lighting can be adjusted with bulb changes, additional lamp fixtures, scrims, etc, or ND filters. Obviously this is more work than just turning the iris to f-8 to chop 1 stop of light.

Effect of Short Shutter Angle On The Look Of The Film

If you use the shutter control to chop that one stop of light, the resultant moving picture image(s) will also be changed. The shutter's angle is now at a shorter angle of 45 degrees and can now impart a "stuttering appearance" onto the film depending on other settings. See "Saving Private Ryan", or The Gladiator", for examples of short (45 degree) shutter angles.

Also keep in mind that shorter angles will affect panning rates. Anytime a panning rate exceeds a particular speed/shutter angle/FPS settings, a corresponding condition will be created called "Rolling Shutter". Also known as "The Jello Effect" because of the look of the effect on the finished film. The rolling shutter/jello effect has been with filmmaking since the 1st film camera was invented. Is due to too fast of a pan rate and is 100% operator controllable. Got rolling shutter? Pan slower.

More here:

          http://en.wikipedia.org/wiki/Rolling_shutter

ND filters or gels can also be used over windows to control light. Windowed gels can be used in conjunction with other lens filters to allow sunlight to be shot with indoor film. Or you can gel the indoor lights to match the outdoor light color temperatures coming through windows. With a film camera there is no white balance to correct for off-white conditions, but you can have the film converted to digital format and balance the digital footage if the color is slightly off.

Here's a link with some more info:

     http://en.wikipedia.org/wiki/Shutter_speed

     http://en.wikipedia.org/wiki/Rotary_disc_shutter

And finally, there is a somewhat rude, but technically correct answer, as to the effects of small shutter angles in a motion picture camera:

     http://answers.yahoo.com/question/index?qid=20120306163953AARUh4C