An Experiment in Follow-Spot-ery


Results of ZipLoc bag/Super Trouper test, performed Friday, 08/24/07.

In trying to determine the best way to get that soft “Broadway” feeling in the beams of my Xenon Super Troupers in an arena, so as not to blind ABBA;  I did the following experiments, based on the recommendations of a number of folks at the LightNetwork, as well as a famous Lighting Designer who holds a “New York Lighting Seminar” each year.

I tried in about 2002, in a theatre venue that had Lycian 1290 2Kw Xenon followspots, putting one piece of ZipLoc bag in Frame#6.  I saw no real difference in the hardness of the edge, and so dismissed this as an “urban myth.”  Someone call Mythbusters.

The issue was raised again last week on the LightNetwork, so I got it in my head to try again, this time with more advice from more people.

Then it dawned on me this past week why a baggy in a Lycian 1290 didn’t work—the color frames are BETWEEN the lenses!  It’s like rolling in the “beam flattener” or “homogenizing filter” in an Xspot.  Some operators dislike having the color frames in the middle of the fixture—those who learned on a carbon-arc Super Trouper generally like them there.  The Xenon Super Trouper’s color frames are all the way at the front, toward the stage, I suppose to extend the life of the color media.

So here’s what I did and observed today with one Strong Xenon Super Trouper Long  Throw fixture focused on a black velour drape with 50% fullness, approx. 175’ throw distance.  I wanted to use two fixtures side by side, but the show tomorrow has 4 catwalk positions and 4 concourse positions, so no two lights are together.

 In the shop I cut and framed the following.  Note the RED bags are STORAGE and the BLUE bags are FREEZER.  (The paper labeled ”202” is just there to provide contrast, as the workbench is black.  The CTO and Deep Amber colors are what I removed from a show in last February.  We don’t use house frames very frequently.  All rock/country shows bring their own.

As per instructions I rotated one bag 90° to the other.  I labeled the non-printed side of each bag under the zipper before cutting them apart.

I then climbed the 110 steps to the catwalk spot basket, and installed the frames as follows:  

 Frame#1 had 2 “cuts” of Hefty STORAGE bag rotated 90° from each other.
Frame#2 had 2 “cuts” of Hefty FREEZER bag rotated 90° from each other.  (Engaged in picture above).
Frame#3 had 1 “cut” of Roscolux 132 that I had framed from a previous show

I optimized the 2Kw Xenon lamp in the Super Trouper and focused for a razor sharp edge.  I tried to take a picture from the followspot’s vantage point but my 3.2-mega pixel, 15x zoom, HP735 digital camera just took a black picture.  So I optimized the other 3 lights in the catwalk and called the House Electrician to hold my Light Meter while I ran the lamps in and out to balance the intensities.  When we were done I went back down the 110 steps and took this picture:

 Now is a good a time as any to apologize for the quality of the pictures.  The above picture was taken standing about 20 feet away from the drape.  The spotlight is hitting the drape at maybe a 25° Angle of Elevation.  The drape and carpet are actually very black to the eye.  Incandescent PAR64 1Kw NSPs were providing House Light in the arena, as well as some HID worklights.  There was a sound class and other work going on or I would have made the house completely dark.  I have had this camera for over two years and have taken maybe 50 pictures with it, so Annie Liebovitz I’m not.  My naked eye could not see the Blue Halation seen easily in the above picture, or the fall-off of the beam on Stage Right.  Still digital cameras do make good color temperature meters.

Intensity measured at the center of the beam was 81 foot-candles.  Picture above is open white, open beam, just larger than full body shot.  Built-in flash on camera is OFF.

Now someone had to go back upstairs (guess how many?) to put in Frame#1.  The House Electrician stayed on the arena floor with my meter and camera and a radio to me while I climbed the 110 stairs and put in Frame#1-STORAGE.  He measured 70 FC at beam center and I observed the edge was slightly softer, but still had a defined edge.  What surprised me was that the whole quality of light changed, seemed to get “muddy” and changed color as though ¼ CTO had been added.  The House Electrician took a picture and I bumped to Frame2-Freezer.

The beam edge looked exactly the same as STORAGE to me, and had the same “off” color and quality, but did look lower in intensity.  Beam Center measured 40 FC, a 50% reduction.

I then rolled to Frame3-Rosolux 132. 

TEN times fuzzier!  The light scattered everywhere and I couldn’t even determine an edge anymore.  This is the problem I’ve had in the past:  even the lightest frost Roscolux makes is too much.  [Update.  While adding the Rosco link I found Roscolux #140: Subtle Hamburg Frost NEW! 2005.  Well where have I been?  My latest Roscoux swatchbook is dated as "Rec'd 10/04" so I guess I didn't get any at last year's LDI.  Update those swatchbooks regularly folks.  But be sure to save the old ones.  I wish I'd kept my Cinemoid and Gelatran and Roscolene books, if only to reminisce over extinct colors!]   The beam measured 75 FC, brighter than the STORAGE and only slightly less than No Color.  I didn’t expect that.  I figured with all that spread we’d have to lose intensity.  Note that I did not touch the Iris, Douser, Trombone, or any other controls on the fixture, except for the boomerang to change “colors.”

I then moved the X132 from Position#3 to Position#6.  That appeared to make no difference, proving that it doesn’t matter which slot the frame goes into.  I’ve had people tell me it matters whether the “shiny” or “dull” side of R119 goes toward the lamp of a Source4, or that the L202 MUST go outside and the frost inside, but I just can’t see it—other than for consistency’s sake.

I told the House Electrician we were done and he asked if he should review the pictures before I shut down the lamp.  I told him that was an excellent idea.  He told me my camera had 16 pictures but 9 and 10 were black.  Those are the one’s I took while at the spot and I knew that and should have deleted them, but I didn’t.  He also told me I was getting a low battery warning and I told him I’d been getting that all day.  I put fresh Panasonic Digital batteries in last night.  One of the reasons I don’t use the camera that often is that it eats batteries, particularly cheap rechargeable.  So that’s why I have no pictures of the STORAGE or FREEZER; you’ll just have to take my word for it.  Sorry.

Hefty brand Storage and Freezer bags did not work for me.  Maybe it does have to be ZipLoc brand.  Whatever Brand of single layer of bag I tried 5 years ago in a Lycian 1290 did not work for me.  I still want to try GAM10-30, maybe Joe Tawil of GAMproducts will send me a free sheet if he reads this.  If/when I get other diffusion media, I’ll repeat the experiment and be sure to get pictures.  I’ll make the House Electrician go operate the boomerang, and I'll take the pictures.

My advice to all is to experiment in YOUR venue with YOUR fixtures, and once you find what you like, stick with it.  Until you’re persuaded by someone on the LightNetwork or ControlBooth to experiment again! 

Wed., 03/12/08: So this past weekend I was forced to again put a baggy in a followspot.  This time a Xenon Gladiator III.  It didn't work any better than the last time.  The R132 looked much better.  But after coloring five spotlights for the show, the entire thing was done in Open White.   It is what it is.