Diffusing gel for LED's

[paulnick]

Hi, I'm lighting a children's show using half a dozen LED's. They will be located about 2 to 3m from the children and I want to use a diffusing gel so that the point source of the LED's is not directly visible but only a coloured disc is seen. It It won't matter that there will be some reduction in brightness but I would prefer not to increase the beam angle too much. I have seen the suitable gel demonstrated at White Light to great effect but we can't recall what it was (that is White Light or me). If anyone could help I would be grateful.

Many thanks

 

Wildswan

[top-cat]

251 Quarter White does increase the beam angle a bit but not as much as a full frost would. That is what I have used before. Although remember it does steal a bit of your intensity.

 

 

http://www.leefilters.com/images/diffusion-no-filter.jpghttp://www.leefilters.com/images/diffusion-251.jpg

 

[J Pearce]

As there is no heat you don't necessarily need proper gel.

I once nicked a load of the fluorescent tube diffuser that comes as a sheet during a refurb, worked brilliantly for this sort of thing. Tracing paper can work well too.

[top-cat]

As there is no heat

 

Careful. Some of the bigger LED sources do actually get pretty hot especially when they've been on for a while.

 

Remember if you're using an LED source because you can change it's colour, it will spend far more of the night switched on and thus generating heat, than a tungsten fixture where you're switching fixtures to change colour.

 

I'm not saying the wear is equal. I'm just saying it's not non-existent either.

[litemog]

As there is no heat you don't necessarily need proper gel.

I once nicked a load of the fluorescent tube diffuser that comes as a sheet during a refurb, worked brilliantly for this sort of thing. Tracing paper can work well too.

 

A hire company once forget to send me the bespoke diffusion lenses for some Colour Block DB4's. I ended up using the bubble wrap that the units were wrapped in. Worked surprisingly well.

[alistermorton]

We've used Scotch magic tape as a diffuser on some led battens. Works surprisingly well.

[mattlad564]

yes, you do need to watch the heat. the internal components of nearly all LEDs do build up heat over time.

 

 

[Wingwalker]

You can use Lee400 although depending on the intensity / type of LED units you are using it may be necessary to have a slight curve across the front plane to soften up the output.

[numberwrong]

By it's very nature diffusion will widen the beam angle.

If the LEDs are being used for back light, and you don't want the audience to see the horrible RGB light source then I'm afraid you're never going to completely get rid of it. I've used Lee 250 half diffusion on led pars and batons when up (or down) lighting set to stop colour separation near the light source. However when you look directly at the light RGBs are clearly visible.

You could maybe use some very heavy diffusion but to even get close to the look of a PAR you'll probably have to use 2 pieces staggered some how by about an inch apart.If you do this then you'll have a very wide and very soft beam.

There's a reason that you still see PARs used for back light on rock and roll stages. LEDs aren't there yet (although if you've got cash to burn then they're close!)

The alturnitive recommendations for diffusion sound interesting and would be useful to use for testing or to use in an emergency but diffusion is very cheep and you can reuse it even in conventional fixtures so why bother with anything else?

 

[top-cat]

If the LEDs are being used for back light, and you don't want the audience to see the horrible RGB light source then I'm afraid you're never going to completely get rid of it

 

 

If this is the only problem, the answer is fairly simple and is there already.

 

There are plenty of manufacturers doing COB (Chip on Board) LED PAR Cans which use a single high-power (often 150W+) LED chip so it's a single light source mixing the colour. In this scenario, it's obviously not the same as a real par can but far closer than your common units containing multiple light sources.

 

http://prolight.co.uk/images/media/ELUM101/ELUM101-wr0.JPG

 

[sleah]

^^^^^^^^ That looks the ideal candidate to be the back end of an opti-par. Presumably being single light source, the beam angle can be altered with pretty much the same lenses as opti-pars?