projection speed change between 50Hz and 60Hz

[Jay Schwartz]

Wow, I'm surprised I did not already see the answer to the initial questions. So here we go...

U.S. power is at 60 Hz, and will definitely affect your motor speed compared to 50 Hz.

As noted, many projectors, including Bell & Howell, have two pulleys for speed change. Sometimes they offer a choice between 18 and 24 fps (when connected to the correct power source for the motor installed), and others -- such as the military spec Bell & Howell projectors, and every Elmo or Eiki projector I've ever owned, offer two pulleys that will run the projector at 24 fps on either 50 Hz or 60 Hz power.

If I shift the belt on my Elmo to the 50 hZ pulley and use it here in the USA, it will run FASTER than normal, not slower.

[John Eickhof]

the belt pulley issue was addressed by myself and others early in this thread, if you read the thread you will find that the tq3 model machines are 50/60 hz without mechanical change as they are driven by a dc motor with electronic variable dc drive, thus no belt or pulley changes are required, best to read through the entries before assuming something. we do love input from all here, so i hope you keep active if you have something to contribute or need advice. the tq3 is quite a versitile machine for a bowell and growl...

[Jay Schwartz]

the belt pulley issue was addressed by myself and others early in this thread, if you read the thread you will find that the tq3 model machines are 50/60 hz without mechanical change as they are driven by a dc motor with electronic variable dc drive, thus no belt or pulley changes are required, best to read through the entries before assuming something. we do love input from all here, so i hope you keep active if you have something to contribute or need advice. the tq3 is quite a versitile machine for a bowell and growl...

It's true that I did not notice the post about how this model adjusts electronically to different power sources, so I apologize for that. However, I did not see anyone else explain that some dual-pulley 16mm projectors may have 18/24 fps pulleys, and others have 50 Hz/60Hz pulleys, so I wanted to make that clear. I've seen examples of similar model Bell & Howell projectors with both options.

[John Eickhof]

very good point, later machines generally only had mechanical adjustments for line frequency and the sound silent was optional, originally 16mm was the amateur film format thus silent was very prevalent until 8mm took the home market. and speed change was simply mechanical. the TQ series was designed with europe in mind and the adjustable line mains and variable speed was a great solution to make it a universal machine. and yes you are correct on the line frequency speed differential, years ago i worked in a small circuit of single theatres, one had century projectors and soundheads, ironically the movies ran about 15 min shorter in time than when they played at another house that had rca soundheads with super simplexes, i finally figured out the century soundheads had 50 cycle pulleys! i changed out both machines with 60 cycle drives and the shows ran at proper running time! of course the owner gave me guff since now he didnt get to go home as early as he used to!

[Floris Vanhoof]

Thanks for all the info!
I'm just back from 7 screenings in Canada and the U.S. and glad the speed stayed the same.
I was especially happy that the throw in a 300+ seat theatre in Montréal was still ok.
The rest were smaller venues and in Brooklyn, NY the projector was standing on a ladder to shine over the heads of the standing audience.

For my next series of shows I’d like to build a single blade shutter into my B&H TQ3 16mm projector.
Does anyone have any idea where to find these kind of shutters?
Ideally, these would be for sale somewhere.
Or which older model projector would have a compatible single blade shutter?
If this is impossible, the shutter needs to be custom manufactured.
Would this be as simple as cutting one blade off my dual blade shutter? Or does this yield to unwanted effects?
Are there any standard single blade shutter designs around?
Years ago I removed the shutter of an Eiki projector for special effects with external shutters, but for sync and portability, I’d like the shutter of my B&H projector inside.
Did anyone here switched shutters in 16mm projectors?
Ideally, as the shutter is in the middle of the projector and someone in Europe who's experienced with putting back together and finetuning wants to do this for me.
All advice welcome.

[Emiel de Jong]

As far as I know single blade shutters don't exist for this series: since there normally was no use for them. I guess your model has a 2 blade shutter: technically the best solution would be to remove one of the blades and re-balance the shutter with some weight to compensate for the missing blade. What I heard about this series is that they are very complicated to re-assemble though... However: when you have a machine that can be missed anyway you could try to cut one blade off without disassembly of the machine, and just see if the result is workable. (Not too much shaking of the machine after the operation and not too fast wear because of the instability).

[John Eickhof]

a good sheet metal shop can cut a blade, depending on how it mounts you will need a hub and you MUST add counterweight to balance for the missing blade! otherwise the bearings ill fail rapidly. why do you want a single blade? i would thin flicker with the original shutter is bad enough at 10 frames/sec? are you thinking of enlarging the blade size for more cut off time? all that will do is cut down light and not reduce flicker unless you are servo driving it? interesting concept i would like to see what you are trying to achieve and why take it on a road show?

[Floris Vanhoof]

I would like to achieve more flicker as an experiment to see how to overload our perception.

[John Eickhof]

ahh! interesting, i'm pretty sure you may find your goal! I would suppose length of retention foe the illusion of motion will vary somewhat person to person though...

[Floris Vanhoof]

any links to or info about single blade shutter designs, shapes and sizes is very welcome.

I'm currently reading "A STUDY OF FLICKER IN 16-MM PICTURE PROJECTION"
http://ia601608.us.archive.org/8/ite...39socirich.pdf

[Paul H. Rayton]

Hi, Floris -- Thanks for the link, but in case you didn't realize it, That link takes one to a web source that requires downloading a complete 422 page document. I started waiting for it, but it was simply going to be too much data, so abandoned it. Plus, I might not know where to find the specific article (unless the link ultimately took me there -- but, still, I didn't wait that long.) Any chance you can summarize it, or post the relevant page(s)?

And I'm wondering if you're pushing the limits of "flashing" lights with possibly-unsuspecting members of an audience? Photosensitive epileptic seizures can be triggered; in many commercial locations where such flashing is likely to happen, warnings are posted. Are you researching that issue, trying to provoke it, or something else? If you're just "playing around", you should at least be aware of the potential for unanticipated reactions.

[Floris Vanhoof]

I am aware of this and sings will be posted.

[Randy Stankey]

You're likely considering things, already, so I'm just thinking...

What is your goal with this project?
Are you studying the limits of projection speed and flicker for various people? Are you just trying to do something cool? What are you trying to find out?

My concern is that most people won't tolerate low frame rates that produce jerky images and lots of flicker. Even for an audience that doesn't have neurological issues that make them extra sensitive to flickering light, you're likely to get a lot complaints. The caveat would be if you have an audience that came to watch such a presentation and knew what they were going to see.

I think that is wrong or even immoral to subject an audience to a presentation that would make them uncomfortable to watch. It only causes fatigue.

When I was taught projection, it was part of the operator's duty to ensure that the movie which people were paying to watch was in focus, properly framed, free of jitter and didn't have a flickering picture.

Ever since I was a kid, I remember people saying things like, "I don't want to watch a movie in that theater because, every time I do, I walk out with a headache!"

Most people don't recognize certain flaws in a movie presentation like flicker or jitter. They might notice it, at first, but they quickly learn to ignore it. However, after two or three hours of watching the show, their eyes get tired and they start to get a headache or they have bleary vision but they don't know why. All they know is that they didn't have a good time.

If a movie projector jitters, it will produce an image that jumps up and down by a tiny amount, perhaps imperceptibly to some people. But, all the while, their eyes are subconsciously jumping up and down in order to track the jumping image. After two hours of that, anybody would have a headache!

As I am sure you are aware, a similar effect happens with a flickering image. Eventually, the audience will tire and they will suffer negative effects, even if only excessive eye strain.

Anyhow, I believe that it's the projectionist's job to prevent things like that from happening.
It would be like ordering food from McDonald's and getting cold french fries. McDonald's fries are supposed to be piping hot! (So's the coffee but that's another kettle of fish! )

If the whole purpose of the show is to have a flickering image and a jumpy picture, that's okay as long as the audience knows it and that's what they came to see. If people think it's "old fashioned" or "edgy" looking, so be it. Do people want to smoke weed and get zoned out watching a flickering movie? When I was in college, people use to get loaded and go to the planetarium at the Boston Museum of Science to see the Pink Floyd laser show. It certainly is one way to spend a Saturday night... If you're into that sort of thing...

Just so long as you aren't subjecting an unsuspecting audience to that kind of fatigue.