Source Fours & Chroma-Q colour scrollers

[vbm]

Hi Blue Roomers-

 

Does anybody have any experience of using Chroma-Q colour scrollers on Source Four profiles? I'm planning to use four Source Four profiles (19 or 26 degree), ideally with 750W bulbs, with Chroma-Q colour scrollers, to light a large(ish) mirror ball I have on a job next week. It occurs to me that with 750W bulbs, and the profiles shuttered down onto the mirror ball, I might have a hot spot hot enough to melt the scroller (I've had unfortunate, messy and expensive "learning experiences" with PAR 64s & scrollers before- 500W good, 1kW bad, or longnose good, shortnose bad!) I'm guessing it will probably be OK with 575W bulbs, but I'd prefer to use 750W bulbs.

 

Anybody have any thoughts based on experience, good or bad?

 

I thank you.

 

VBM

[gareth]

Should be fine. As long as you're not putting too much of a peaky "hot-spot" into the beam, you'll be OK.

 

You could also consider adding a piece of Rosco heat shield to the back of the scroller - it works wonders. Just take the backplate off, put a square of heatshield under it, and hold the heat shield in place with the screws as you re-attach the plate. And make sure you're using HT versions (if available) of any Lee colours in the scroll.

 

Another trick, if you're using a particularly dark blue, is to have two adjacent frames of the same colour and move slowly back and forth between them while the light's on.

[mbthegreat]

For a production just last week did exactly this, Source Four Profile shuttered down onto a mirror ball with a scroller infront (don't know what brand the scrollers are sorry). We were using the 575W lamps, and had absolutly no problem

[vbm]

Thanks folks, I've got some Rosco heat shield on order from AC Lighting and I'm going to give it a go with the 750W bulbs. Its a gig in a tent so it should be relatively cool (especially with the weather we're having at the moment!)

 

I'll let you know how I get on.

 

VBM.

[Neil Hampson]

I was under the impression that the source 4 was a 'coolbeam' lantern, like the strand SL, if so, are we really worried about a gel melting in a scroller.

I'm sure we all use scrollers in front of PAR64s, and conventional lanterns without any problems, I certainly do. I have also been known to use shortnose PARs without heatshield and I am still on my first set of gel strings. There seems to be a bit too much caution in the advice here, it's not as if the application is an installation that's not going to be touched for 6 months.

The fans inside almost every scroller will help enormously in dissipating the heat from the gel surface (providing the scroller is fitted the right way in the lantern, not sideways) and the newer models offer a 'wiggle' feature that move the gel slightly continually to avoid any possible hotspots hitting the same part of the gel continuously

 

regarding the shuttering issues, shuttering off the lantern at the gate is reducing the amount of light and therefore heat from the front of the unit, the lens system is not concentrating the light into a hotspot just because the shutters (or iris) are used. I can understand if you wanted to have 5-10 deg optics, but the gel runners shouldn't be anywhere near a focal point for the light output.

[dirkenstein]

I used this combination on out last show, specifically with S4 26 and 36 degree 750W fixtures. ChromaQ CQ1 scrollers are fine on S4 750W, even without heat shield- provided the scrollers are powered! There is a continuously-running fan that prevents the gel from overheating. If you bring the S4 up full without the scrollers powered and the fans running there is a risk that dark colours (especially deep blues seem sensitive to this) will start melting at full brightness. This is also a good reason to ensure the start of your gel string is clear or a pale colour. The heat shield should protect the gel string to some degree in case of fan or scroller power failure-I haven't tried this myself but lots of people seem to confirm this provides extra protection.

 

I've always wondered- doesn't this result in the heat shield becoming absurdly hot though? I mean if you were absorbing all of the IR spectrum from the lamp your 10 grams or such of gel would be absorbing maybe 700W of thermal power. I think even glass might melt rather fast at that absorption rate. Even at 50% absorption from a 35% efficient fixture the heat shield would have to absorb over 100W of thermal power- totally unrealistic. Just consider the size of the heat sink on Selecon Pacifics, where most of the IR winds up not going down the lens tube.

 

So does Rosco heat shield reflect IR? Or does it do something more basic?

 

The description on their web site distinguishes between Thermashield, which seems to be some sort of multilayer IR reflecting film, and Super Heat Shield, which 'reflects convected heat'.

 

So is normal heat shield just some sort of clear temperature-stable gel that traps convected heat from the fixture away from the gel? Or is it something more clever?

 

How IR-transparent is gel anyway?

[vbm]

I was under the impression that the source 4 was a 'coolbeam' lantern, like the strand SL, if so, are we really worried about a gel melting in a scroller.

I'm sure we all use scrollers in front of PAR64s, and conventional lanterns without any problems, I certainly do. I have also been known to use shortnose PARs without heatshield and I am still on my first set of gel strings. There seems to be a bit too much caution in the advice here, it's not as if the application is an installation that's not going to be touched for 6 months.

The fans inside almost every scroller will help enormously in dissipating the heat from the gel surface (providing the scroller is fitted the right way in the lantern, not sideways) and the newer models offer a 'wiggle' feature that move the gel slightly continually to avoid any possible hotspots hitting the same part of the gel continuously

 

regarding the shuttering issues, shuttering off the lantern at the gate is reducing the amount of light and therefore heat from the front of the unit, the lens system is not concentrating the light into a hotspot just because the shutters (or iris) are used. I can understand if you wanted to have 5-10 deg optics, but the gel runners shouldn't be anywhere near a focal point for the light output.

 

I have used scrollers in front of PAR64s with and without problems, and when its me buying the gelstrings in the first place, and replacing them if/when they break/melt, I don't think "too much caution" is a bad thing! Not to mention the minor issue that if we melt our gelstrings onsite, we lose our groovy mirrorball effect.

[LeeStoddart]

I frequently use ChromaQ scrollers on the front of 750W Source4 36 and 50 degree lanterns without any any "melting" issues. (I use the smaller 5" Broadways on S4s)

 

Making sure that the scrollers are powered up before the lanterns so that the fans are running is probably the most useful piece of advice.