Wide angled projector

[glenn@KC]

Hello,

 

I’m having ‘issues’ with projection and was wondering if anyone has any ideas.

I have to project on to a large screen with little space to play with. So far I just have a small image in the centre and was thinking I could increase the size by using mirrors. I guess bouncing the image off a mirror will make the distance the beam travels grater and the image larger.

 

Just wondering if this has ever worked before and though calling on the experience of the blue room users might help.

 

If anyone has any comments or suggestions I would be really grateful

 

Hope you all have a good weekend

 

Glenn

[live]

Get a short throw lens as the more the image has to travel the more the o/put is decreased

What make of projector is it?

g

[Tilt]

Hello Glenn,

 

It can be done, for best results use a optical mirror. A normal mirror has 2 reflecting surfaces wich result in a double image.

I have found 2 websites with info

 

http://www.screen-tech.de/index.html

http://www.pgo-online.com/intl/katalog/list_mirrors.html

 

Succes,

 

Allard

[henny]

the more the image has to travel the more the o/put is decreased

g

 

eh? a 1:1 lenes on a 5m wide screen at a 5m throw would be just as bright as a 2:1 at 10m on the same screen.

 

the amount of light will only decrease if the screen (image size) is bigger.

 

mirrors are often used to help with lack of throw, they must be front silver or you may get a dubble image,.

 

the normal trick is to have the projector on the floor shining up at a mirror that then directs the image at the screen.

 

ian

[Tom]

We did this recently with a "normal" mirror with no noticeable double imagining - though it was with images and not with text which may be more sensitive to this.

 

I found that getting the projector and mirror in the correct place helped immensely. We positioned the projector immediately below the screen (pointing up stage) with the mirror parallel to the screen. This reduced the need to do any key stoning - which again would reduce you image size.

 

T

[Stuart91]

I also have used a bog-standard mirror when we have been caught out with a restricted throw distance. There wasn't any noticeable double image. Get the biggest mirror you can find, we had what I would think of as a full-size mirror and it only just fitted. We were shooting onto a 10ft wide screen and the mirror was approx 1/4 of the way along the projector throw.

 

Also, don't forget to clean the mirror, especially if you are in a dusty venue with several day's worth of shows.

[Rikio]

We do this often on gigs - we do a lot of work in schools where there are limited distances for rear projection.

 

Our mirrors are big - 4'x3'- and weigh a ton - but allow us to halve the throw distances for our 6x4 screens.

 

They are just standard mirrors with the silvering on the back, but I've never noticed and image doubling.

 

They are mounted on a custom designed mount, which lets us prop them at any angle, but the ideal way I've found to do it is to place the projector just below the bottom of the screen and keep the mirror fairly horizontal. Some of our projectors dont have keystone - so I have to get the projector in the right place to avoid any distortion.

 

Rikio.

[Stuart91]

They are mounted on a custom designed mount, which lets us prop them at any angle,

 

That sounds like a very good idea. The few times we've had to employ a mirror, the biggest hassle has been getting them propped up at the appropriate angle.

[Andrew C]

The few times we've had to employ a mirror, the biggest hassle has been getting them propped up at the appropriate angle.

I'd add to this that a Nobo flip chart stand and gaffer tape are perhaps not the best method for supporting mirrors. Cue loud SFX and 7 years bad luck! :D

[gyro_gearloose]

If people are getting good results with normal glass mirrors, why not try some Acrylic mirror? You'd get the same result but at a fraction of the weight, and no risk of seven years bad luck if you drop it :D

[Toxopholist]

Try speaking to Mark at Anna Valley about where he gets the mirrors for his mirror bounce jobs, they are a silvered film on a metal frame, I believe he gets them from a supplier in France. Very light and easy to use, but be aware that the surface is ruined with the first fingerprint A little care means you get several uses for them. I think that is what Gyro means by an Acrylic, unless he is thinking of a silvered acrylic sheet, which has been tried, and is a nightmare to get flat.

 

One thing to watch for, learnt through bitter experience, is there is no such thing as "just a mirror bounce" it takes an unbelievable amount of minor adjustment and patience, CDUK used to be a 20foot wide screen with a 4 foot wide mirror, "just to turn a corner" and give us an extra 3ft of throw, on a good day to get an acceptable geometrically accurate image would take the best part of an afternoon.

 

What I am saying I guess is if your are just attempting to project an abstract image it a reasonably easy and quick fix, at a push I have even "borrowed" the mirror from my hotel room to get an extra couple of feet of throw, but if you are trying to project a coherent content critical image then you need time, a plan, and to invest in a decent mirror. As to doubling projectors through a mirror, it is easier to have 2 mirrors, but you need to triple the time it takes you to get a reasonable doubled up image, and I have done a blend through a mirror, and that took the best part of 5 hours to get the physics and geometry right, never mind starting on the colours.

 

I hope this hasnt put you off, the more you practice the faster you get, its not impossible to to get a perfectly correct image, it just takes patience.

 

Take care

 

Charlie