Is there a correct shutter blade setting?

[Fred Hess]

I tore apart an old Bell and Howell Dual 8 projector to give it a good cleaning. I'm hoping to eventually use it in my capture process. I got it all back together but now when playing a reel (Super 8) there is a darkening of the video. It will play just fine for a while, then suddenly get dark for a bit, then back to normal. This continues for the entire reel. I tried a different reel and the same thing happens. My first thought was that I somehow moved the shutter so that the blades aren't consistently lining up correctly. Is that even possible? If so, is there a certain position the blades should be set? Or should I be looking at another cause for this problem? Thanks.

[Nantawat Kittiwarakul]

Does that "darkening" shows up ONLY on the video?
When projecting films in normal manner how does it look to your eyes? The reason I'm asking because this seems more like the camera's incorrect settings, rather than the projector's fault to me. So if that darkening shows up even when looking with projected image then that's indeed the projector's fault.

[Ed Gordon]

It might be that the shutter needs to be adjusted:

Here is a video on the basic operation of movie projectors:

[Fred Hess]

Thank you Ed! Good info for this novice tinkerer. I was able to take the projector apart again and found that indeed, the shutter needed adjustment. There was a blade covering the gate every time the sensor fired. Once I moved the shutter about a third of a turn it opened up the gate nicely. No more dark shadowing!

[Alwyn Adkins]

What a brilliant video by Bill, and what an incredible mechanism.

[Ed Gordon]

Thank you Ed! Good info for this novice tinkerer. I was able to take the projector apart again and found that indeed, the shutter needed adjustment. There was a blade covering the gate every time the sensor fired. Once I moved the shutter about a third of a turn it opened up the gate nicely. No more dark shadowing!

That is great news Fred. You have torn down a projector and reconditioned it. You are more than a "novice tinkerer"

[Nantawat Kittiwarakul]

So you're really scanning your film with frame-by-frame method right? Cool, that's getting more interesting. Would like to see how your setup works then.

[Fred Hess]

Nantawat, no, this is the projector taken from my old Tobin system, which has a real time capture method. On the motor shaft there is a plastic disc with a piece cut out of it. Opposite that is some sort of sensor. So as the shaft turns, once a revolution the sensor encounters this blank area of the disc. I don't know what this setup is supposed to do since I can't figure out what the sensor is triggering. It appears the wiring leads into the camera area, but since the unit isn't frame by frame capture, it's a mystery to me. I do know that when the sensor sees the blank part of that little disc, the shutter blade has to be clear of the gate or I get the dark shadow. If I ever feel the need to tear it apart again, I'll take a picture and see if you can explain it to me.

Meanwhile, the frame by frame project is still something I want to do. I'm trying to learn as much as I can before installing a stepper motor in the projector and figuring out what camera to use. I've been so busy lately this project has been put on the back burner but hopefully I'll get back to it soon.

[Nantawat Kittiwarakul]

Ah, that ole school telecine unit.

Never actually owned any of those projectors. But my wild guess is that that disc is part of its servo contorl for the main drive motor to keep it runing at the perfect sync speed, and in correct phase, with its built in camera unit. Still don't fully understand however that if it can be adjusted to be "in phase" with the camera unit, why it had to be a shutter blade there too? Sounds too redundant and unnecessary to me.

[Stan Jelavic]

If the camera provides the frame sync out and the disk provides the motor speed feedback and then cct that compares the two. At one point in my telecine "career" I considered building something like that using the sync separator IC and Arduino to control the motor.

[Fred Hess]

Thank you Gentlemen. You are both more knowledgeable than me in all this and I now realize that this unit is "tuned" so that the motor and camera are in sync with each other. While the Tobin is "old school" in that it will never produce a resolution higher that 720p, it is just so convenient and reliable and the results are always good. It did have a problem with jittery results but after giving it a good cleaning that seems to be much better now. I put together another unit using a Sankyo projector with a 3CCD camera. I've been toying with it and soon (too busy with VHS and MiniDV and 8mm transfers right now) I'm going to create a comparison video which I will post here. The new unit should produce a better video but I'm real curious to see the results.
I already know that my pieced together system requires a lot more time and attention (and wires everywhere) than the Tobin. I wish someone would create a system that is as easy to use as the Tobin, but produces higher resolution video. I'm surprised that no one seems to have come up with something that records 2K or 4K in real time, doesn't require the flipping and cropping, is easy to focus, reduces the duplicate frames, etc. I've often considered swapping the Tobin camera with something like a PiHQ camera but I don't think I'm qualified (smart) enough to pull that off. Maybe with some help it could be done. Might even be an inspiration for others.
Sorry to go off on this tangent. Just thinking out loud. Anyways, thanks for the input!