Side Masking: Independant Control of Masks?

Gregory-

I've designed both a single and a dual-motor system. I would say that the dual-motor approach is easier to implement from a mechanical standpoint. The drawback is of course having to incorporate an extra motor and controller that is more sophisticated.

Independent control is not neccesarily an advantage, but you get it for free.

Don

I am planning a motorized masking system and will have them independently controlled. Just my preference. I just think it will be simpler to operate, so if, like a previous poster mentioned, you have a rare title that is a bit off-center, you're covered. I'll just have to have left and right buttons on my Crestron.

I don't think the mechanics are any easier with dual motors, in fact, the contrary. My commercial system uses dual motors, but as Don said, you require a far more complex controller. And depending on how you intend on setting position stops (mechanical or electronic) also introduces another challenge. Dual motors require synchronisation for movement, but at the same time require independance to set offset positions.

For a DIY solution, I'd be going for a single motor using pulleys and belts - easy to synchronise, less complex controller, single stop, less components so cheaper etc, etc...

Cheers,

Chris

My DIY masking system uses a single motor for the left/right masks, and a single motor for the vertical up/down masking. That way I can exactly mask any format of film. Single motor left/right masking is much easier to implement than independent left/right masking. I have had no problems with pictures not being centered on the screen, so I see no need at all for independent control of left and right masking panels.

A few years ago, I did a mock up of a concept system known as "Gull Wing" which was essentially two hinged doors to cover the side pillars of unused screen. It worked well and I have been thinking about doing an AT version. Just wondering if anyone else did anything similar and if it would be possible to automate it?

Synchronization of a dual-motor system is difficult. I would say that it is not necessary, but it loses that WOW factor. For that reason, I prefer the single-motor approach. There's nothing cooler than watching both masks move in perfect unison.

BUT, this means the addition of belts and cables, that make it more complicated mechanically. Plus, you need to add torsion springs inside the rollers.

So, it is a trade-off. If you're not bothered by the fact that each mask is not synchronized with the other, than the dual-motor system is the easiest to implement.

Don

Wow, that's a very unique and innovative approach Mark. I have never seen such a system deployed but I see no reason it would not work. Only drawback that I can see is that you would lose the WOW factor of having the masks slowly moving out to reveal that great CinemaScope picture- something that always blows away my audience!

Gregory-

I'm still trying to come up with a need to have both masks move independently. The dual-motor system allows this, but it is just because the left and right mechanisms are not connected to each other.

I would be surprised if you can find two motors that run at exactly the same speed. With encoders on both motors, you can control position and speed , but that's where you need more complex electronics.

You can jog the masks in a single-motor system. If you have presets, then the jog function is only needed for initial setup.

Don

Thanks Taffman The manual prototype version I made in 2006 used hinged MDF panels and was a bit heavy. When closed, the screen looked like a regular 16:9, then when I opened the masks, suddenly there was the wow that only scope can bring.

The main reason I believe independant control is valuable is mainly in the initial setup stage. Very rarely does anyone get the projector in exactly the right position, so having independant control allows you to "fine tune" the setup. Granted, once it's set for all masking positions, you should never have to touch it again, so the use is limited, but still worthwhile IMHO.

Also, I've been able to achieve dual motor synchronisation, but by doing exactly what you've said - using dual motors each with high resolution encoders.

Cheers,

Chris