Burnt-out LEE filter

[ash.beck]

Hi all,

Any idea what could cause this to happen to a Lee filter (pic below)?

I was using it in a P64 short-nose floor can with a 500W MFL lamp. The fixtures were powered for a few hours (4 or five) and were several meters away from any surface in front of the business end.

 

This happened in 3 out of 4 of the cans, 1 purple, 2 red. The red was from a brand new sheet of gel, the purple from a sheet I've been using in our own par cans from some time (but a fresh piece).

 

This happened in hired cans, but the cans appear to be working fine.

 

Any ideas? I've never seen Lee filter behave like this after such a short use... I've only seen really ancient bits of Gel back when I was at school that looked all warped and cracked.

 

http://farm5.static.flickr.com/4038/4660847933_b297deba84_m.jpg

[mac.calder]

It is common on non-HT gel in short nosed pars that are left on for a few hours. It is even more common in saturated colours which need to "discard" a lot of the light output from the pars.

[GridGirl]

Mac's right - to solve it, either buy some heat shield gel and put that between the lamp and the gel, or get HT gel which won't be so susceptible to burn-out.

[gareth]

Several factors working against you here - the cans are short-nose, so the colour is much closer to the lamp than with normal cans ; they were on for several hours at a time ; the colours are pretty saturated (if the one in your photo is anything to go by) ; and I'll hazard a guess that it's not HT colour. So basically, what you've experienced is pretty much par for the course - that's why colour falls under the heading of 'consumables', it doesn't last forever.

 

Can you swap to long-nosed cans? Can you get Lee HT versions of the colours that you need (or a Supergel equivalent)?

[Smiffy]

Could I hazard a guess that the cans were pointing straight up too? Heat rises after all....

 

Cheers

 

Smiffy

[professor]

Agreed, from your description it seems perfectly normal to me.

I saw someone once try same thing with Congo and it lasted about 3mins in a 1k.. So he splashed out on some glass dichcroic gels (not cheap) but he did the same effect every other week so was feasible expense.

[david.elsbury]

The problem with dichcroic glass is that as you move off-axis the colour can shift, so it might be a nice blue in the centre, but with purply edges.

[ash.beck]

Thanks all. I was a little worried!

I don't use short-nose cans very often (especially not floor cans) so haven't experienced this kind of melt before in a short time. Was particularly worried because they were only 500W lamps, and having used the same gel for much longer periods in (hung, long-nosed) 1000W pars with no problems seemed a touch odd.

 

Will get some heat shield if I use them again, although I think If I do the same thing again (back-lighting a white drape for a ball) I may use something else, like a few Codas.

 

Anyway, thank you all for reassuring me!

[Don Allen]

If you read up on the history of the Parcan in Concert Lighting, the initial design was a short can and the gels burnt out too quick so they ended up with a long can with ventiliation holes and an air gap behing the gel frame.

 

The cyc lights will be a better choice for an even wash for the white drape. If you look at the different makes of cyc lights you will see different ventilation designs used and gel life varies as saturated gels need ventilation to survive, helped by heat shield.

[john deans]

" saw someone once try same thing with Congo and it lasted about 3mins in a 1k.. "

In one venue I worked congo Blue was renamed Burnout Blue