Image sound separation

[John Burgess]

Often wondered why Super8 image sound separation was only 18 frames compared to 56 of standard 8. The farther away the sound stripe from picture gate and intermittent reduces unstable audio. There must have been a reason 18 frames was chosen, wondered if any members have any ideas
On this subject ?
Off topic, hope all UK members are enjoying
the wonderful weather !
John

[Osi Osgood]

That's an interesting question, which I have no answer to, but I would like to know the answer, to be sure.

[Brian Fretwell]

I wonder if Kodak had the idea of sound film cartridges for sound on film cameras in mind when they developed, idea 56 frames would make the construction much more difficult and unwieldy than just 18.

[Maurice Leakey]

I wonder if Kodak had the idea of sound film cartridges for sound on film cameras in mind when they developed, idea 56 frames would make the construction much more difficult and unwieldy than just 18.

I am sure that Brian is correct. It certainly makes sense. The sound cameras could also use a silent cartridge, but not vice versa.

[Melvin England]

I have also thought about this situation over time, but from a reverse angle.

56 frames separation seems excessive. What the reasoning was, I don't know. I think in introducing super 8mm they brought the separation in line with professional films thus 18 frames separation (not to be confused with sound films at 24fps/silent at 18fps). I was always lead to believe that 18 frames was the closest they could achieve where the film, after the stop-start-stop-start motion in the film gate, was back to running smoothly over the optical or magnetic sound systems, thus producing smooth consistent sound.

I am happy to stand corrected on these technicalities if I am wrong.

[Steve Klare]

I wonder if at least part of the reason is the plan to market Super-8 Sound as a home movie medium.

OK, so it's 1973 and we've shot Auntie Marge's 80th birthday with Super-8 sound cartridges. Let's say we're frugal and we choose to shoot 18FPS.

After we get the film back, we decide that scene of Uncle Bob calling Uncle Jim insulting names really has to go (Uncle Bob had a few too many. He apologized the next day, but we didn't film that...), so we cut the offending frames out and splice the adjacent scenes. Because of the seperation, we get residual sound from beginning of that deleted scene (right up to where Uncle Jim punched Uncle Bob and you stopped the camera.) right where the splice is.

At 18FPS with 18 Frames seperation we get 1 second of stray sound, something like "OOOOOFFF!!!"
At 18FPS with 56 Frames seperation, we'd get a little more than 3 seconds, something like "-always thought you're a OOOOOFFF!!!"

(-Aaaah, Memories!)

In motion picture production, sound was normally separate from image until much later in the process, but being that this was sound on film from the start and due to the seperation of the gate and the head, you were stuck with the sound from one scene being right next to the image from the one before. As soon as you cut and splice, you have that odd interval where the sound and the image don't belong together, and all you can do is shorten it, never eliminate it.

[Maurice Leakey]

....56 frames separation seems excessive. What the reasoning was, I don't know...

The answer is simple, it is double the picture/sound head spacing of 28 frames for 16mm magnetic sound film.
That is, of course, the same length of film in each case.

[John Burgess]

Thanks Maurice I never thought of that , probably because I have never had any 16mm mag film.
John

[Maurice Leakey]

On 16mm, the magnetic head obviously has to be slightly ahead of the optical pick-up. Optical has 26 frames separation from the picture gate.