Annie is fully redundant, at least from a projection point of view. Let me explain what I mean. Theatre is all about repeatability and redundancy. In order to protect the show against every reasonable trouble it may face, we develop systems of redundancy; from understudies to duplicate props and costumes, we all create methods of safeguarding the show against failure. In the case of projection design, we have a few common methods of doing so.
As one of Wendall K. Harrington's associate projection designers (along with Michael Clark), I usually use one of three basic setups. Of course, there are others out there, but I almost always use one of these three that I call: The cold spare, the understudy, and full redundancy. In a cold spare situation, you have your system, and each of the major components has a spare that sits unused during the show. If something breaks, you fix it when you can, but it doesn't always mean that it can be fixed during the show.
Using an understudy system, you might have a component like a projector or a media server that is connected to the system and ready to go into the show in case of failure, but during normal show conditions, it doesn't actually do anything. The understudy system is better than a cold spare, but I still don't like it as much as using full redundancy.
In a fully redundant system, you have a complete duplicate of your entire media server and display system. If something fails on the main system, you flip a switch or take a specific lighting cue, and the video system changes over to use the backup.
Sometimes when we are operating in a full redundancy, we still want to get a little extra brightness out of the projection system by using the backup projector converged perfectly to the main projector. In that case, you get nearly twice the brightness when everything is working correctly, and if a projector is out, you have your original brightness.
The problem with this, which we encountered and expected on Annie, is that projectors can only converge in one plane at a time. What I mean is that, if you have two projectors pointing at the same surface, and they are in focus and aligned all the way downstage, they won't be aligned and in focus further upstage. You have to either adjust the video content being fed to each projector so the correct parts of the image align, or you have to physically change the settings on the projector lens.
We attempted to make it work on Annie by aligning the projection lenses electronically mid-show. The idea was that, before each cue, we would send the command to align the images optically to the surface they were on. I have to hand it to Christie Digital, as the manufacturer really wants to make it easy for us. The projectors we used have a command language that lets you send a command to it over the network, and it will change its lens settings. You hook up the projector to the same network as the media server, in our case, Dataton Watchout, and you have the media server send a command to the IP address of the projector.
For example, sending the text (SHU 1) tells the projector to close its shutter, which is necessary for black outs. Unfortunately, the commands that control things like lens zoom, focus, and shift are not 100% reliable for converging multiple projectors. Christie specifies that they are accurate to +/- 2 pixels, which actually is excellent for single projector displays. I can live with being one or two pixels off when I'm just trying to fill a space with one projector.
However, for aligning two projections to the same surface, +/- 2 pixels is too high of a tolerance. If one projector is two pixels to the right, and the other is two pixels to the left, that is a difference of four pixels, and that just makes a blurry double image. In the end, we had to scrap that idea, and we decided to focus the projectors on one plane only, and we only ended up using both projectors at the same time on that one surface, the rear cyclorama.
I look forward to the day that multiple projector lenses are completely controllable and can recall presets with predictable and repeatable results, but I haven't seen it yet.
Projection Designer: Wendall K Harrington
Associate Designers: Daniel Brodie, Michael Clark
Programmer: Paul Vershbow