Projecting onto a curved screen

[Big Dave]

I saw exactly what your needed at PLASA, just can't remember who it was. They were right opposite the central bar (hick) to the right of VLPS. ok, so not much use unless you've kept your program.

 

If not, a couple of old 3 gun CRTs (Sony 1272, Barco 808 styley) are relatively simple to focus on circular screens - not that I've done it for about 5 years but it does work. Only draw back is the total lack of light output (sub 1000 ANSI) and the fact that anyone who still has them in hire stock may have to spend a few days blowing the dust off.

 

Best people to speak to would be ETC

[Martin]

Bryson, this is probably just possible. We recently had E\T\C in doing what I thought was the impossible. 5.7m between back wall and cyc, projecting a 10m wide image using two projectors crossing. The difference between the furthest point and nearest point of each image was 2.7m, and they got it pin sharp! apparently a few years ago this wouldn't have been possible as the lenses didn't exist. Okay granted these weren't video projectors but they were using Barco 0.9 wide angle lenses, which were originally designed to be mounted on Barco video projectors.

 

Whether you end up using video or film projectors, you are going to be dealing with flying some large projectors.

 

The production was 'The Saint of Bleeker Street' and there is an article about the productions projection in 'Entertainment Technology' Issue 65, 4 Sept. Should be available for download soon at etnow.com

 

More dimensions (for each projected image that were merged):

Image width: 6m

Furthest throw distance: 6m

Nearest throw distance: 3.3m

 

As Big Dave said, have a chat to E\T\C about it.

 

http://www.goodman50.fsnet.co.uk/images/pigi.jpg

[Bryson]

That was a Arnim Freiss job, was it not? I went to college with him. Wonder if anyone has his number....

 

That's kind of encouraging, anyway. Production meeting is tonight, where we'll see if it's at all possible within the budget. (Which, judging by the fee they've offered, may not be enough...) Please Barco, if you're listening...sponsor us....

[Glyn Edwards]

I may have Arnim's number round here somewhere. He did a job with us at Easter time. If you want it let me know by PM and I'll try and dig it out.

 

Glyn

[mark b]

I know what you are on about. The technique is called soft edge blending. And I am working on a show that uses this for a 16:9 rear projection screen. PM and I may be able to help.

[Bryson]

Just a quick update:

 

The show was this week. In the end, I ended up with a bit of a bodge (as you do, like) to make an approximation to what it could be... (Sadly, we kind of ran out of time to rustle up sponsorship, and Barco pulled out...)

 

So, some of the projectors (four different projectors!) didn't quite fill the screen, and I realised (too late) that what I really needed to do was get the project file off the video chappy and distort it in Final Cut to suit the venue...oh well, I'll know for next time.

 

The interesting thing was that focus wasn't really too much of a problem, despite my fears. The real issue was the barrel distortion effect of the centre of the screen being further away than the edges. As I say, next time I'll pre-distort in FCP3.

 

So, overall, it wasn't a total disaster, and the director knows that if we ever do it again, it has to be with the proper kit.... (so if anyone knows anyone that might sponsor it...Sanyo? Christie? NEC?..) it may well be going on a smallish European tour, subject to funding. (Although the funding people apparently loved it..!)

 

So, overall not as bad as it seemed it might be, and certainly do-able with the right kit. Just watch out for the barrell...

[Andrew C]

Sorry if this seems like a hijack, but I have been asked a linked question for a similar show.

 

Some time back a question was asked on projecting video on a curved surface, and the answer was, "Yes it can be done with a three beam projector, Barco or equiv, by using a custom alinement".

 

I have been asked if it can be done with a 'standard' LCD, if you 'pre-distort' the image. My instinct is no, and that there would be problems with focus too. The screen in this case would be a simple curve in one plane.

 

Anyone got any thoughts?

 

Moderation, moved to this topic from "Live Video Projection at Rock Music Night"

[Bryson]

A highjack indeed! So I've dragged this topic from the depths of the Blue Room and breathed new life into it.

 

So, in my experience, if you're not extremely fussy about pin-sharp images, it is kind of do-able. I was lucky with the above project as the images were quite "abstract" and without any particularly sharp images or fine detail.

 

The pre-distortion is more work than it sounds, though! Better get rendering now...

[TomLyall]

Not something I've ever seen or heard of being done, but I have seen a similar technique used with a camera for a 360 degree angle.

 

Basically, it involves rigging the projector either lens up, or lens down, and using a conical mirror to reflect the light onto all of the screen, from the one projector. I imagine it would require a really bright projector. :huh:

 

Again, this is something that would require a huge amount of preperation in terms of rendering the image etc, but it might work a hell of a lot better than seperate projectors.

[the kid]

What I've seen before is a fish eye lense and one or would that distort it to much ?

 

and it was for a dome shape.

[Andrew C]

Fish eye lenses produce a very wide beam, my (no, not my) problem is that the edges of the screen will be further from the lens than the centre. This means that something will be out of focus.

[timmath]

I can't offer an answer but I can give you an example....

 

Take 'The National Lottery Jetset' TV program as an example... from memory... there is a 180 degree screen, about 10m radius and 6m high the upper and lower sections are split between an upper flown ring of 8 projectors and there are 8 floor projectors for the lower ring - all are 3k ish projectors. These are all matrix'd from a video wall controller (compashite in and out)

 

The source material comes from one catalyst, through a scan converter, and various colour correctors.

 

Up close the image is OK, it's not great but then it's designed for camera.

 

Regards

 

Tim

[slim_mcslim]

you could always try one of these

 

 

slim

[PeterJ]

Interesting topic and hopefully I may be able to add some of my own experiences.

 

My company "Joys Production Services" have quite a few years experience of widescreen projection and processing, being one of the only companies in Europe to stock the Montage and the recently released Spyder widescreen processing systems. We have done a number of curved screens - the most recent for the Labour Parties conferences in Brighton and Newcastle, so do speak with some authority.

 

You actually have anumber of issues here:-

 

An 8m radius circle will give you a screen width of just over 50m (2*Pi*r). If you think of it now as just a flat wide screen of 50m x the required height of 4m you have a screen of 12.5:1 ratio.

 

If we want to fill that screen edge to edge then you could place 4 projectors equally from left to right, but would have to over-fill vertically to fill completely left to right. Ive worked out that using XGA projectors would have 4048 (4 x 1024) horizontal resolution but only 325 pixels of actual vertical resolution. Considering standard def video is 576 pixels vertical resolution, you are at about half that. If you want to keep the vertical resolution of the projector on the screen you would actually need 10 projectors. Butting projected images together does not make for the illusion of one seamless screen, so a little overlap would be required. An overlap of 150 pixels would allow you to cover the screen with 11 projectors. This would give a pixel space of 9764 x 1024 pixels.

 

So now you have the resolution on the screen, you need a system that can distort the image at the edges. The only box I have had any faith and good results from has been the Folsom Screen Shapers, and one would be needed for each projector! This is how we did the curved screen on the Labour Conference - and a big well done Simon Cox from Blitz who supplied them and set them up. Our curve is not as tight a curve and we only used 3 projectors wide to give us an image about 17m x 4m but the theory is the same. One downside - The Screen shapers add about another 1.5 - 2 frames of delay to the system, so you do have to watch what other processing is being done with PPU's, TBCs etc. (see Spyder below)

 

On to the processing - 11 outputs fed to 11 projectors would require Spyder processing. Montage would have been the answer 12 months ago, but Spyder is now becoming more capable and cheaper. The Spyder processing boxes come in different flavours, varying with the anount of input and output channels.... from a simple 3 input 1 output, to a 5 input 3 output unit. The units can be joined together so it would be posible to have a unit that would give 12 outputs with as many live simultaneous inputs as required or as budget would allow. The 12th output would give the operator the ability to see the complete output in Preveiw and Program on one monitor.

 

The Spyder system can handle that resolution with ease and would allow live inputs to be placed and moved around the screen. Each input can be computer:- up to 2048 x 1200 resolution or video:- either standard def or HD. Spyder has the ability to clone its inputs to produce more windows so you could have 12 images from only 6 inputs. Also Spyder can support loading in of stills at that high resolution and then mixing the background. We have used triple head computer displays giving us a resolution in excess of 3,800 pixels, and I see know reason why multiple units could not be used to increase this resolution if required. The capabilities of Spyder now allow us to use it as a vision mixer, therefore allowing the minimum of processing throughout the system. The addition of the new live panel hardware desk further enhances the ability of Spyder and shows why the system is one of the best in its class. If anyone needs any further info I would be happy to oblige.

 

Peter Joy

Managing Director

Joys Production Services

[mikienorth]

Not quite useful enough but there is, or was a company called Creative Technical Services who did a lot of nightclub installs for Rank/Allied Domecq, and I saw them install a 360 degree screen above a dancefloor in a club in Leeds in 1998. The club was called Evolution, it's a while ago now so I guess things have changed, but they used, I think, 12 small sony LCD projectors to do this, past that I am in the dark, but it was quite a while ago. I watched Manchester United in a european cup match on it one night,one minute 12 screens, the next all one, but very streched for a TV signal. On opening night the absract images, and the Ally McBeal dancing baby worked well though.

I'll try to track a site for the company down, it'd make this more useful.