Date: Tue, 22 Apr 2003 22:16:40 +0000 (GMT) Subject: [tf] well, that almost worked Remember when I was noodling about cyc lights a while back? I later plunged ahead with a somewhat odd design for lighting one, and figure I'll plow the results back into the general body of knowledge here. The problem was to light a huge roll-down projection screen against the upstage wall of Kresge, to serve as a backdrop for the South Asian dance/culture show last Saturday. The show, btw, ran quite smoothly and well and I think all concerned were pretty happy with it. During planning/rehearsals I was telling the dance group coordinators to think of the backdrop as a big pixel, to which sent values of R/G/B would create eye-fooling color mixes to almost anything they wanted. This year I wanted to avoid having a groundrow of striplights like we did last year, and try to give that small bit of stage real estate back to the dancers at the expense of a little more real estate at the sides. More of the dancers would thus be silhouetted against the screen, in theory, creating a less visually interrupted presentation. So I decided that despite various warnings against lighting a cyc from the side because it tends to emphasize wrinkles, I wanted to light from the side. This is a projection screen, not a cyc, so the wrinkle problem is considerably less. Whatever units I was going to use would obviously have to side-hang off a vertical boom, so striplights were more or less out. After reading a few specs on cyc units I figured that side-hanging individual one-cell cyc units would be the way to go, and checked with the ALPS people where the rental would come from whether they thought that was okay. After some yelling around the shop they didn't really anticipate any problem with it -- there's enough venting around the edges of these things that there would still be plenty of airflow around the lamp even with the gel on. The other nit was that the screen is 20ish feet high, so the vertical distance would be rather large. I didn't need to go *all* the way up, but enough to get well over dancer height. I assumed about three units per color per side, making nine units up each pipe. It turns out that they actually have single 16 foot lengths of pipe, which we agreed might be stronger than using couplers. The weight distribution was going to be a little odd, but probably not dangerously so -- and as it turned out the center of mass of a unit with its C-clamp mounted on the pipe is just *inside* the edge of the base. We biased sandbagging in favor of the lighter side of the base, and of course safetied each pipe to the overhead grid with ring-tops and rope. The head facilities guy there, an old rigging/theater type himself, insisted that the rope and pick point had to be rated to take the entire load with a standard 5x safety factor, in the event that for instance the threads at the base simply failed and the whole assembly suddenly became free-floating. Because of the potential proximity of the lights to the drapes, we also hung a layer of fiberglass cloth mat called z-tex [?] in between. This stuff normally hangs just upstage of teasers, to protect the soft goods against the hot ass ends of lights hidden behind same, so of course this 40-foot length of stuff had its grommets against the *long* edge... we had to make do and slide it almost halfway over an overhead pipe and clamp it in place so the long end hung just to the floor between the drapes and the lights. And fiberglass of course is itchy in a way that stays with you long after working with the stuff, until you finally get to a shower. Plan view upstage wall ___________________________ / ----------------------- \ <-- projection screen / O-< >-O \ <-- broad cycs, pipe base /.===== =====.\ <-- velour blacks & z-tex // \\ <-- blacks continued // \\ <-- blacks continued // \\ // \\ / \ As it was, this scheme took a certain amount of stage real estate at the corners that some of the larger groups possibly would have liked to have back for dance space. But nobody crashed into the trees, so they obviously dealt. And the lights were nicely hidden away. The whole thing was a bit tedious to put up, and 25 x 20 foot hunks of velour are *bloody* heavy, but it looked pretty nice once up. The lights were wired into very convenient stage-pin wall pockets near the bases, so the longest jumper needed was maybe 10 feet. Each color got three 500W units per side, so they could 3-fer together into one dimmer for a total of 6 channels to run the whole mess -- RRGGBB at the board. Usually I ran the same levels at both sides to create a single cyc color, but for random things like intermission stage-warmers I could play with different colors in each side and get some interesting fading across the screen. L&E broad-cyc lights are *very* broad in their output. At one point I just hooked one up to power and waved it around at the wall to really see its pattern, so after that I knew what I was up against. Coverage up and down the sides was very even -- you couldn't really see where the individual instruments were throwing from. Horizontally was more or less okay, but not as even or bright as I would have liked. As much as I tried to aim the hot spot at the center of the screen, it was definitely brighter at the edges as might be expected. At lower intensities the middle of the screen was definitely dim. It looked best at high intensities in single colors. Mixes still got across but somehow emphasized the lack of coverage at the center a little more. All this was partially because these units are designed to be six or so feet from their target surface at a much steeper angle, and I had them maybe at a third of that to still try and throw over 10 feet out, so naturally it wasn't going to be optimal and I expected this. There was also a certain amount of spill heading downstage, but I managed to minimize that angle by sort of using the drape edges as barndoors, and what escaped was promptly absorbed by the opposite black. The beam had a definite vertical edge, or shadow where the linear filament's output passes the frame of the unit, and a bit of tweaking was needed to line up all those beams at the outer edge of the screen to form a single smooth vertical line with no funny color variations along it. I also evidently out-did myself with the basic front wash this year -- 12 instruments per side, yielding the best and brightest wash I've ever gotten in that space, but it was bright enough that scatter and bounce back up off the stage was tending to overpower the cyc sometimes. I managed to compensate somewhat by having an inhibit submaster on the more upstage channels so I could ride it and dim down that area just enough to let the cyc punch through better. This also helped mitigate the drape edge shadow problem [remember Balticon??] that the curtains unavoidably presented when trying to light upstage areas. The gel cuts are of course quite large, like 10+ x 12 inches, and one can obtain exactly four cuts from a reasonably standard sheet with very little left over. I used R26 light red, L139 primary green, and R68 sky-blue instead of the "normal" cyc colors which tend to yield less output. Silk wasn't needed at all; the completely unfocused lamp and "pebbly" reflector gave plenty of diffusion. Overall I'd say it more or less worked, with a few nits, but would have worked better on a narrower backdrop. 30 feet or so is just too huge. And now I have much better experience with cyc units that I can pass along to anyone else that it might help. _H*