# 'Stacking' Projectors Horizontally



## staticblanket (Apr 29, 2019)

Hello!

I'm fairly new to the world of video and the venue I work in has recently acquired two 14k Christie projectors. 

The setup in our booth has necessitated installing them around 4-5' apart and I've noticed when I overlay the images on each other that there is a slight difference in horizontal scale or stretch due to the different angles they are shooting onto the surface. 

I can tweak the keystoning so that the difference is minimal, maybe a few pixels on the test patterns at centre. The difference isn't really apparent when an image is displayed but I've had a picky video artist go crazy over it. 

Can anyone please offer any tips on how to resolve this problem?

Thank you.


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## Amiers (Apr 29, 2019)

Push them closer together if you can. Then have them shoot parallel to each other. 

So if they are like this / \ then your gonna have a tougher time than if they were | |. Then you could just do a lens shift and not keystone which like you said doesn’t line it up exactly.


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## ruinexplorer (Apr 29, 2019)

Make sure that both are exactly perpendicular to the screen, then use the lens shift to align them. Any digital alignment such as keystone correction will distort the image.


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## RonHebbard (Apr 29, 2019)

staticblanket said:


> Hello!
> 
> I'm fairly new to the world of video and the venue I work in has recently acquired two 14k Christie projectors.
> 
> ...


 *@staticblanket* Idle curiosity; where are you: Hamilton Place, Aquarius, Mohawk??*? *
Toodleoo! 
Ron Hebbard (Who was born and raised in Hamilton, lived in Burlington for 35 years and is presently retired and residing in Waterdown.)


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## staticblanket (Apr 29, 2019)

@RonHebbard I'm at Hamilton Place. Your reputation precedes you, sir. 

Original intention was to have the projectors in the house but Audio objects to the fan noise. Inside the lighting booth, as you know, there are two windows off of the centre line of the room, one of which is full of lighting monitors. Maybe someday in the future I can move one of them over the lighting desk to achieve better symmetry but for the time being I was hoping there was some tweak to horizontal scale I could use.

Thanks for the responses.


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## RonHebbard (Apr 29, 2019)

staticblanket said:


> @RonHebbard I'm at Hamilton Place. Your reputation precedes you, sir.
> 
> Original intention was to have the projectors in the house but Audio objects to the fan noise. Inside the lighting booth, as you know, there are two windows off of the centre line of the room, one of which is full of lighting monitors. Maybe someday in the future I can move one of them over the lighting desk to achieve better symmetry but for the time being I was hoping there was some tweak to horizontal scale I could use.
> 
> Thanks for the responses.


 *@staticblanket * 
*a*; Can you stack your PJ's one above the other so they're the same distance SL of the centre line*?* 
*b*; I'm *Ron* (NEVER sir.) to everyone, from dogs to my great granddauhters. 
*c*; Say hello to Cindy Anderson Jennings, Mike Stewart and Greg Kott for me. 
Toodleoo! 
Ron Hebbard


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## RonHebbard (Apr 29, 2019)

staticblanket said:


> @RonHebbard I'm at Hamilton Place. Your reputation precedes you, sir.
> 
> Original intention was to have the projectors in the house but Audio objects to the fan noise. Inside the lighting booth, as you know, there are two windows off of the centre line of the room, one of which is full of lighting monitors. Maybe someday in the future I can move one of them over the lighting desk to achieve better symmetry but for the time being I was hoping there was some tweak to horizontal scale I could use.
> 
> Thanks for the responses.


 *@staticblanket* Who are you really*? * (And are your dues paid*??*)
Toodleoo! 
Ron Hebbard


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## Amiers (Apr 29, 2019)

Are they shooting straight on or do you have them at an angle. It’s easy to T them up to your screen or atleast to each other. At that distance even an inch is killer if your projectionists are picky.


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## Jay Ashworth (Apr 29, 2019)

When you say "overlay them"... do you mean "edge join" them to get a 32:9 image, or do you mean "co-focus them" to get a 16:9 image twice as bright?


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## ruinexplorer (Apr 29, 2019)

This would be a stacked image (both images occupying the same space for increased brightness) based on the description.


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## staticblanket (Apr 30, 2019)

Hi again, 

Thanks for all the continued support. To clarify the situation I've attached a napkin style drawing of the current setup. It seems to me the only solution is to move one of the projectors over the lighting desk to achieve a better geometry. The projectors are in stacking rigging frames but if I stack them vertically the lower projector is easily blocked by seated patrons. 

For this application it's about 150 ft. to the projection surface.


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## RonHebbard (Apr 30, 2019)

staticblanket said:


> Hi again,
> 
> Thanks for all the continued support. To clarify the situation I've attached a napkin style drawing of the current setup. It seems to me the only solution is to move one of the projectors over the lighting desk to achieve a better geometry. The projectors are in stacking rigging frames but if I stack them vertically the lower projector is easily blocked by seated patrons.
> 
> For this application it's about 150 ft. to the projection surface.


 *@Amiers * and *@ruinexplorer* For those playing along at home: The rectangular lump on the centre-line is a concrete column with conduit and ventilation ducts in it, thoughtfully placed on the centre-line by the architect during construction in 1971 opening in 1973. 
Toodleoo! 
Ron Hebbard


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## Amiers (Apr 30, 2019)

You could try to invert the right one and get the lenses closer together. 

That is a trick position. But you should be able to lend shift the left one right and the right one left to center everything and avoid keystoning all together. Whatever you do don’t angle them towards the screen. Make sure they are perpendicular as best as you can. 

In that setup you will want to make sure the projectors in the racks are plum to each other all the way around.


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## Footer (Apr 30, 2019)

staticblanket said:


> Hi again,
> 
> Thanks for all the continued support. To clarify the situation I've attached a napkin style drawing of the current setup. It seems to me the only solution is to move one of the projectors over the lighting desk to achieve a better geometry. The projectors are in stacking rigging frames but if I stack them vertically the lower projector is easily blocked by seated patrons.
> 
> For this application it's about 150 ft. to the projection surface.



I don't think I could have come up with a worse start for overlaying projectors then that.... both off center and separated. I'd build a vented and isolated box on the front of that concrete collum, put them in there, and call it a day. Not what you want to hear... but if you are close now with keystone then that is the best it can be until you can move them to actual center line. The fact that you can even get them close in that configuration is amazing. Stacking projectors and keystone is never a good solution.


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## ruinexplorer (Apr 30, 2019)

Also, if you must use keystone, then your best practice is to get "perfect" alignment optically between the two projectors prior to digital correction. This way, your digital correction is the same, making it less apparent to the designer.

While I agree with @Amiers about inverting one projector in order to get the lenses closer, this may not be practical if there is no means of leveling the inverted projector. Plus, with that distance, it shouldn't matter much.

Is airflow the reason for the horizontal separation between the projectors? If, like some projectors, the airflow is front to back, try to get them closer together. That should make it easier to know that they are parallel with each other.


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## Amiers (Apr 30, 2019)

My reasoning for inverting was to make shifting less extreme. As I feel like he’s maxing out his lens shift.


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## staticblanket (Apr 30, 2019)

The current position of the projectors has to do with the following configuration for our orchestra:

In which I butcher the image quality so badly with keystoning I am embarassed to admit it on this forum. Perhaps foolishly I had settled on a position that could work both configurations with minimal effort as sometimes we have minimal time or labour to reconfigure.


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## Amiers (Apr 30, 2019)

Sounds like you need two more projectors for the Orchestra positions.


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## staticblanket (Apr 30, 2019)

Cellphone shot from the lighting side on a recent show. The tips are much appreciated.


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## RonHebbard (Apr 30, 2019)

staticblanket said:


> The current position of the projectors has to do with the following configuration for our orchestra:
> 
> In which I butcher the image quality so badly with keystoning I am embarassed to admit it on this forum. Perhaps foolishly I had settled on a position that could work both configurations with minimal effort as sometimes we have minimal time or labour to reconfigure.


 *@staticblanket* OMG that's phuquing _UGLY!!!_ 
Toodleoo! 
Ron Hebbard


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## ruinexplorer (Apr 30, 2019)

Amiers said:


> My reasoning for inverting was to make shifting less extreme. As I feel like he’s maxing out his lens shift.



Totally agree if the throw was shorter. At 150', that shouldn't make much of a difference. But since the feet are only on the bottom, the inverted projector would no longer have any means of adjustment (unless it is in an external stacking frame). That can cause a number of issues.


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## Amiers (Apr 30, 2019)

He did stay they are in a frame. But we don’t know if it’s a full on adjustable stacking frame with the ratchets. 

Frankly from that picture I think you are doing a banging job for the shitty angle you are shooting it at. 

This is one of those catch 22 where you say the truth and nobody listens til an outsider says the same thing and you get yelled at for it even though it’s outside of your control.


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## Ancient Engineer (May 4, 2019)

Oh deary dear...

If this _has_ to be done...

The simplest solution is to block off the offending audience seats. Vertical stack and sleep at night.

Get some backup from the SM to get the Audio peep marching with the rest of you.

If you are stuck with this awfulness...

Like mentioned above... get the lenses perpendicular to the screen center.

Physically move the projector lenses as close as they can be to each other.

IF somebody is complaining then you need to get the SM and _all_ the complainers in the same room so that the best compromise can be made...


Decision making in a situation like this is always a challenge. But everyone has to be at the same place and time to hash it out.


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