Long lasting filters

[ojc123]

I've searched Blue Room/Wiki/Web but the problem with searching is knowing what you are looking for.

 

I run a school lighting system which I use in a fairly basic way commensurate with my limited knowledge. We have various generics which are largely in a standard state except for the annual production.

 

I have a few fresnels and floods which I would like to have as colour. I get fed up going up and changing the filters every week or two. I've tried various brands and some are better than others. The spiky wheel to make airholes helped as did lowering the levels a bit and putting the gels in the further away slot of the two.

 

I'd like a fit and forget solution. Does such a thing exist? Thanks.

[pritch]

Tried HT gel?

 

There's also dichroics, although see this thread for a fairly lengthy discussion on the pros and cons

 

http://www.blue-room.org.uk/index.php?show...mode=linearplus

[Barney]

You will find that darker (or more saturated) colours tend to "burn out" faster than light, paler colours. This is mainly due to the amount of light that is 'stopped' by the colour filter. Very saturated colours need a lot of different wavelengths of light to be stopped, allowing through just the very specific colour that you are interested in. The light that is stopped effectively ends up turning to heat, and can melt the gel as you have seen.

 

That's maybe an oversimplified description, but you get the idea!

Solutions:

 

Have you tried fitting Super Heat Shield or similar between the spotlight lens and the colour filter? This can certainly help extend the life of your gels when used correctly (you need to leave a gap - as big as possible - between the heat shield and the gel). The shield reflects infrared (heat) energy from the lamp before it gets to the colour filter, extending the life of the gel.

 

It's available from Stage Electrics (this product), amongst others.

 

A longer lasteing, but much more expensive, alternative would be to invest in some coloured glass filters, such as those manufactured here by Lee Filters, or ROSCO. Again, thay are available from Stage Electrics, White Light, and the other usual suspects.

 

I've not had much experience with these, other than fitting them in some mini floods used for architectural puposes in a lecture theatre. They seemed to work well then, were fairly expensive, but this was outweighed by the time/cost for the college electricians to come out and change filters every week or so!

 

Others here may well be able to offer better first-hand knowledge of these (glass filters, not college electricians!).

 

Out of interest, which spotlights are you using, and how powerful are they? Do you have them on for a relatively long time each day? It should be possible in a school environment to come up with a solution using the heatshield option.

 

 

Hope that helps,

Barney

 

Edit: must type faster!

[Brian]

You don't say what lanterns you are using but something to watch on the cheaper 'generic' units is the gel frame. On a lot of these they use a punched sheet metal frame with quite large areas of material left to form a 'mesh'. The mesh is there to make the unit CE compliant (OK, it's an attempt) but when in contact with the gel it increases the rate of burn through. The colour frame supplied with things like S4PAR clones is an ideal example and these suffer horriblly from short gel life. The workaround is to use the original frames in the rear gel slot and to use real ETC frames for the gel in the front slot.

 

The other thing to look at would be to get the gel further away from the lamp/lenses by using colour extenders.

[daemon]

Also make sure with your Fresnel's that you haven't got them at full flood. Always a sure fire way to burn out gel.

[ojc123]

Thanks for all this. I've something to research now. Dichroics don't look good for my purpose.

 

They are ADB fresnels. The mesh is not part of the gel frame so I don't think that's the issue. The gel is very close to the lens so the colour extenders may be worth a look.

 

I'll be looking at the physics to see why full flood burns them out quicker. They are used on full flood most of the time.

 

Thanks again.

[david.elsbury]

I'll be looking at the physics to see why full flood burns them out quicker. They are used on full flood most of the time.

'Cos the lamp + reflector is fully forward, closest to the gel :D

[GridGirl]

If you knock the fresnels just a bit back off full flood, you shouldn't see too much of a difference in the size of the beam, but it'll make a difference to your gel life.

[gareth]

The bottom line is that, unless you go down the dichroic glass route (which is very costly and which you've already determined isn't right for you), colour filters will always be a consumable item. There are things you can do (which have already been mentioned in this thread) to help them last longer - use Lee HT instead of regular Lee, use a Supergel or Gam alternative (both last longer than regular Lee), use a colour extender, move the focus of fresnels back a bit from full flood, use a ponce wheel to perforate the colour, etc. - but sooner or later you're going to have to be replacing the filter if you want to maintain the original colour over a longer period of time. It's just a question of how often.

[Barney]

May not be too helpful, but a lower wattage lamp would also help reduce heat (but also light output).

 

Using a 500W lamp instead of 650W (or 1K instead of 1.2k) may assist.