# Top hat on a projector?



## cvanp (Oct 23, 2009)

Hey everyone -

I've been working on projection for Rent (I'll post more about our solution to control in a few weeks) and hit another problem.

Thanks to the amazing Vectorworks 2010 projector features, I have been able to figure out the exact projection placement in advance. This is ridiculously useful and is just blowing my mind in terms of being able to know exactly what we can do in advance.

Unfortunately the main projector screen needs a 38 foot throw using the lens we have in stock. We had wanted to RP it, but we only have about 25 feet for the RP. We can't afford a new lens, so I'm advocating putting the projector in a FOH cove position.

The way our coves are designed though is not great - we have always had trouble with visible light on coves. We have better results with top-hatting though, and can usually eliminate it, if we're careful.

So now I'm curious - has anyone ever used a top hat-like accessory on a projector? I wonder what that would do for us -- if anything at all.

Just a curiosity- never heard about this before. Maybe there's a reason 

Thanks!

cvp


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## seanandkate (Oct 23, 2009)

I've never heard of a top hat as a purpose-built accessory, but it sounds like a great home-made solution for your problem. Or you could price out a lens _rental_ if you really wanted to go RP.


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## cvanp (Oct 23, 2009)

Yeah it would definitely be a purpose-built thing, if we were to do it.

Are there really rental houses that would rent projector lenses?


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## SHARYNF (Oct 23, 2009)

you might want to look at using a mirror so that you can fold the extra 8 feet and still do rear projection. There are a lot of good quality mirrors that are coming on the market (ebay etc) that were used in the older rear projection large screen tv's like Toshiba etc.

The mirror will not reduce the path of the light but MIGHT be a solution to allow you to fold the path and still have it work. Basically you would place the projector facing the rear "wall" , project into the mirror and than have the mirror reflect the imate to the RP surface. 8 feet is not a hugh distance so it might be worth a try. You could start with a standard mirror and them if you get the acceptable size move to a high quality mirror.

Top hat may or may not work it depends on the size of the image beam coming out of the projector. In a different application I was trying to use a Prism multiplexer on a projector vs a source four and it would NOT work

Sharyn


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## Footer (Oct 23, 2009)

cvanp said:


> Yeah it would definitely be a purpose-built thing, if we were to do it.
> 
> Are there really rental houses that would rent projector lenses?



Plenty! Just google it. I have rented from a house in Las Vegas before and they next day aired the gear to me (its cheaper to get it shipped quick then to have a longer rental). I can't remember the company's name, but the gear was good and it came quick.


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## Sayen (Oct 23, 2009)

As a top hat, what about a cone made of blackwrap?


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## derekleffew (Oct 23, 2009)

cvanp said:


> ...So now I'm curious - has anyone ever used a top hat-like accessory on a projector? I wonder what that would do for us -- if anything at all. ...


Never needed one, as video projector lenses are of higher quality and don't exhibit the same amount of flare as stage lighting fixtures.

But as Sayen said, a cone or cylinder of BlackWrap couldn't hurt, provided it doesn't intrude into the beam. I *have* had to apply Blacktak to projectors due to objectionable light leaks, but from the back, top or bottom, not the lens.

And yes, video projector lenses are available from most A/V houses.


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## museav (Oct 23, 2009)

Just be careful that anything you do to limit light spill does not interfere with the projector's ventilation. Many projectors want to have quite a bit of clear space around them for proper airflow.


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## ruinexplorer (Oct 23, 2009)

I'll second the airflow issue. Just being in the cove may restrict airflow where you may consider adding an external fan to move the hot air. I'm not saying this is necessary since I neither know your projector nor your cove. In your projector manual, it should state the distance necessary to be around your projector to maintain proper air flow. If the air flow is blocked, your projector will have thermal sensors to shut it down if it gets too hot. Even if there ample room around the projector, the semi-enclosed space of the cove may build up enough heat to shut down the projector at the most inopportune time.


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## cvanp (Oct 23, 2009)

derekleffew said:


> Never needed one, as video projector lenses are of higher quality and don't exhibit the same amount of flare as stage lighting fixtures.



This is actually quite interesting. The only reason I'm suggesting we might need to figure something like this out is because I was told that projector flare could be worse. It seemed incongruous to what I've actually experienced but I'm new to projection so I didn't question.



I think the moral of the story is maybe I should actually take the projector up there and test it before I make any decisions. If it can be front projected and made to work, that will be a much cheaper option as opposed to renting another lens.


Thanks for your expert advice as always!


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## SHARYNF (Oct 24, 2009)

couple of things to consider most of which you probably have thought of

Rear Projection TYPICALLY is less effected by stage light spilling onto the sufrace

Front projection design needs to be careful about shadows on the image caused by actors or set pieces being in the light path

Sharyn


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