The Lap Dissolve feature on Super 8mm cameras appeared prior to the introduction of Sound Super 8mm cameras. Some Sound Super 8mm cameras stated that you can only do lap dissolves using sound cartridges. This is because the camera does not declutch the film and relies on the design variation of the sound cartridge...which has a ratch mechanism that will allow forward or reverse movement of the film core. Since many of these cameras also use an inner switch to let the camera know if a sound or silent cartridge is installed....the function will not operate with a silent film in the camera.

However...you can 'fool' the camera. You will have to tape a piece of plastic or something stiff over the sound cartridge switch...which is usually to the left of the sound recording head module. This normally activates the capstan drive...but will also let the camera behave as if there's a sound cartridge in the camera. To do a lap dissolve....you will have to initially break the internal ratchet on the silent cartridges. To do this....turn the core counterclockwise a full turn (only when it has a foot of film on it first...so run some film before altering your cartridge!). You will feel the ratchet resistance...just force it past this point...and then carefully turn the core clockwise and counter clockwise a half a turn or so..to make sure the ratchet is not interferring anymore. Then...turn the core clockwise until the filmslack is taken up. Proceed to film normally, and then do your dissolve when you need to.

On silent cameras that offer lap dissolve...the core drive cog is stationary during the fadeout portion of filming...so as to allow a loop of slack film to build in the take up side of the cartridge. This loop is then backwound and shoved back into the supply side of the cartridge...and when you begin filming again...the core takes up the film normall once again. When you break the ratchet....the core can now turn in forward and reverse directions. The purpose of the ratchet is to allow the film to take up snuggly on the core....and when you defeat this purpose...there is minor risk of jamming. However...I have not experienced any problems...and the film transported fine in many test cameras that I tried this out on.

Another benefit of 'fooling' a sound camera into thinking it has a sound cartridge in it...is that it will run more accurately. Many sound cameras ran at 20fps when using silent film instead of at 18fps. So....by 'fooling' the camera it will now run right at 18fps. ONE exception here are the BEAULIEU 3008S, 3008S(MS), 5008S & 5008S(MS) cameras...which DO NOT have a capstan activating switch. These cameras run correctly since the capstan drive is actively engaged regardless of whether or not you have sound or silent cartridges in the cameras.

Final caveat: Doing any of the above is at your own risk. At worst...the dissolve won't work...won't work correctly...or the cartridge might jam. The Super 8 silent cartridge may still not allow a perfect dissolve in your sound camera that was made to do dissolves only with sound cartridges. Also...in many of these cameras' instruction manuals...they will state to only use Kodak sound cartridges for doing dissolves and superimpositions. The only other sound film was from Agfa...their MovieChrome 40 & 160 filmstocks....and though this is all past history now....their internal ratchet design does not allow reverse movement of the film. I was always able to do a dissolve using Agfa cartridges...since I would break their internal ratchet by reversing the filmcore...and then they would work fine. Too bad Agfa doesn't make Super 8mm film anymore....heck...too bad GAF or others don't make Super 8mm film anymore!

Best wishes,
Martin W. Baumgarten

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