Varying the speed of Chinon Sound 7000 Projector

[Le Krok Productions]

I have a Chinon Sound 7000 projector which has a set external speed of 18 or 24fps. However, I would like to know if there is a way internally that I can adjust the speed (shutter) to reduce "flicker" when I capture the image to video? Correct - film speed will/may vary? Though note, I have no concern for sound as I'm only transferring silent film.

Thanks in advance for any comments/advice.

Cheers.

[slashmaster]

A transfer will always look like crap if you're using a 3 bladed shutter. Unless you do it frame by frame you need a 5 bladed shutter. I'm no expert but I think if you're doing it at 18 fps you might need more than 5 blades. I don't know for a fact but you can probably only get a shutter like that for a chinon by fabricating it. Do you have a milling machine and rotary table?

[granfer]

The original poster doesn't say where he is based, so the first answer is not too accurate.
It IS TRUE that " frame by frame" is by far the best way... but a 5-blade shutter is ONLY useful in countries with 60 hz mains frequency, where it will give good results with both 16 AND 24 fps.
A 3 blade shutter can be used for transfers at 20 fps in the USA and 16.667 fps in Europe (50 Hz mains).
A 2 blade shutter can be used for transfers at 30 fps in the USA and 25 fps in Europe.
There is not a lot of point with shutters with more than 5 blades; a 10 blade one would work at 18 fps on 60 Hz mains, but a 25 blade one would be needed on 50 Hz mains!!!!

But, without doubt, for transferring silent film the best results are achieved with Frame by Frame, even with "home-brewed "equipment. Transferring sound is more complex.

[mr_x]

Le Krok needs to know if he has a rheostat or potentiometer controller for the speed of his projector, almost certainly the latter if it is a fixed speed projector. Secondly he needs to know if the potentiometer can be tweaked faster or slower. Some projectors can handle this, others not I think. Thirdly & most importantly we need to know where he's posting from because the transfer speeds / blade configurations are critically different in different parts of the world.

[Lunar07]

OR use the right projector - Just get a Sankyo model. In the USA, many Sankyos go up to 20FPS and have 3-blade shutters, or how about the countless Eumig excellent sound projectors like the S904. They actually have a knob to continuously vary the speed from 18 fps through 24 fps.

[granfer]

The Chinon Sound 7000 is listed in "super 8 database" as having....
"Motor: DC magnetic motor electronically controlled"

There will therefore be, SOMEWHERE in the machine, pre-set speed controls for the two speeds.
I cannot say where you will find them ,or how effective they will be in doing what you want, as I do not know the machine personally.
My earlier post deals comprehensively with the Shutter/Transfer speed relationships for your country.

[mr_x]

Hi,

Theoretical scenario please:-

Someone in the UK tweaks an 18fps projector to 16.667fps, for aerial film transfer to a digital cam. In theory that looks great but I have seen projectors fractionally speed up and slow down, now and then, for various reasons. Now that could ruin your transfer could it not, if you started to get flicker creeping into the project. And you'd be stuck - without a variable speed control. All you could do is dive into the projector circuitry and start tweaking the speed all over again?

Also, if you were doing this 'live' while monitoring for flicker you would be risking electrocution with one hand inside the projector while your eyes were glued to a monitor? How else could you test for 16.667fps?

Have I got that right please and is variable speed control the only real approach to aerial DIY flicker-free film transfer?

Thanks,

Ric

[granfer]

Yes, Ric.
And that's exactly what you do if the speed controls are PRE-SETS. You (if you are competent, or somebody who is if you are not), remove the PRE-SET from the board, fit flying leads and place a control of the same value on the ends. You then place this on a convenient safe mounting, fit a knob to it and use it to fine control the speed for minimum flicker while you transfer. Voilà ! Variable speed control !
This is a common technique which enthusiasts have been using for years.

The best way to do the job is to do it properly.

[mr_x]

Yes, Ric.
And that's exactly what you do if the speed controls are PRE-SETS. You (if you are competent, or somebody who is if you are not), remove the PRE-SET from the board, fit flying leads and place a control of the same value on the ends. You then place this on a convenient safe mounting, fit a knob to it and use it to fine control the speed for minimum flicker while you transfer. Voilà ! Variable speed control !
This is a common technique which enthusiasts have been using for years.

Many thanks - so it's a proper conversion job in other words. I know of a good projector which can be 'got at' speedwise but the conversion is still a totally unknown quantity. The projectors I use are already variable speed models but it would be useful to know how to safely convert pre-set projectors.

Ric

[Le Krok Productions]

Thanks everyone for your posts. As I'm not confident in tinkering with electronics, nor do I have a set-up to create new shutter blades I'll stick to just projecting images. Therefore, any transfers, I'll outsource.

[mr_x]

indeed i wonder if it is in fact possible to vary the speed on a fixed speed projector? you would need to be an expert in electronics. i am convinced that if such a conversion were practicable people would have done it by now and there would be examples on the internet. but get hold of a variable speed projector and you are more or less there. Rheostats can be manually tweaked to vary speed parameters, i have never messed with potentiometers though; although i am told these too can be 'got at'. But don't go tinkering into a live projector - dangerous! Pull the plug first ;)

Heaven for me is a variable speed projector which runs between 16 and 24fps, covering all the recently popular film speeds, but 16fps is hard to find because it is an old speed and old projectors can be a problem - noisy when you live in flats as i do!

good luck

[granfer]

Most "fixed speed " projectors can be speed controlled, and the information is out there if you no where and how to look.

Those that cannot, such as the early Bell and Howell ranges, used electromechanical governors inside their DC motors, so external means of speed control are not really practical.

Those using Synchronous motors, such as true Induction Motors, which follow the mains frequency, can be controlled by introducing a Frequency Inverter into the motor circuit. Expensive, yes, but very effective.

Those using Shaded Pole Induction Motors, such as a wide range of Eumig, Bolex, Prinz etc. 8 mm and Dual 8 mm machines can (contrary to popular belief) be controlled by a simple thyristor based control circuit inserted in the motor circuit, or even in the mains lead. I use such a method all the time.
This latter method is the one chosen by a number of companies offering speed control modifications for such machines. Some even are sophisticated enough to offer LOCKING the speed to the Video camera used for transfer, thus removing the problem of flicker completely.

For those amongst us who also have DIY electronic skills, or have access to friends who have, the details of such a modification (complete with schematics) is freely available.

[mr_x]

Most "fixed speed " projectors can be speed controlled, and the information is out there if you no where and how to look...

For those amongst us who also have DIY electronic skills, or have access to friends who have, the details of such a modification (complete with schematics) is freely available.

mr_x wrote: "you would need to be an expert in electronics."

Thanks Granfer. And as you say, good to have someone in the know. I must say though that I have approached several oldtime experts on ciné projectors and came away with the impression that they wouldn't vary the speeds on a fixed speed projector with a barge pole. If i had a more positive response i would consider farming out various projectors for conversion. I am surprised that some enterprising soul hasn't offered this service on the internet by now?

Can't beat aerial transfers for my money, you get the actual sensation of ciné technology, judders et al

Ric