Directing light from floods

[TomHoward]

I've been trying to light some stained glass windows from the outside for a temporary use (lecture on the windows)

 

I have 8 windows to light. I've tried 400W halide floods on stands outside, just under the window height, and it's okay but I'm losing a lot of light because of the lack of lens.

Is there anything that's worth trying in terms of barn doors, top hats, black wrap etc that is likely to make any difference to controlling the light output and trying to get a little more in the middle, or is it all a complete waste of time?

[empyfree]

You’re probably fighting a losing battle trying to get more light in the middle. You’ll be able to mask light from where you “don’t” want it with some of those methods, but the wastage is usually compensated with heat rathe than any focussing of the light.

[adam2]

Agree, there are several ways to block unwanted spill light, but there is no simple way to increase the light in the desired area.

[andy_s]

Agree with the previous posters, you can mask the light but not focus it. You probably need bigger lights. At my friend's church they borrow a 5kW from a TV company to light outside their east window as part of their Easter vigil. Not being a religious man, I can't speak to the liturgy or theology behind it, but as a lighting effect, it works. (I think it's an HMI, but I'm not too sure)

[bruce]

I guess one of the problems is that the light is directional, and there’s not going to be a huge amount of scatter from the coloured glass - most of your light will pass straight through. To highlight the stained glass, it may be worth trying hanging a diffuser (say a white sheet) outside, and lighting that.

[Whiskers]

I guess one of the problems is that the light is directional, and there's not going to be a huge amount of scatter from the coloured glass - most of your light will pass straight through. To highlight the stained glass, it may be worth trying hanging a diffuser (say a white sheet) outside, and lighting that.

 

+1 for Bruce, its a lightbox effect you need , rolls of diffuser hung outside a few inches from the glass and blasted with a few K, if you have the room for Par cans to diverge to the size of the window frame that will obviate evenness issues. For a long burn or large window when energy cost is a consideration then hire in HMI

[Jivemaster]

Stained glass is best viewed by diffuse light from a sky(!) or other large source, try to have either a big diffuser like cloth or scrim in a light beam but just away from the glass, or a huge diffuse reflector like a sheet(or ten!) of foam polystyrene.

[paulears]

Black wrap certainly acts as a mask, cutting the light, but many years ago, I did an 'arts' project outside and we did a big church with waterproof 300W linear floods. As expected it looks pretty nasty. What we did were make up tubes of chicken wire, then we covered the outside with aluminium baking foil, shiny side in. We stopped it flapping around with lengths of wire, ends twisted together. It actually worked better with the foil crumpled then flattened again. It kind of 'circulars' up the beam, and softens it quite a bit. The output is a bit odd looking, but not like a squared beam linear flood usually is. With an experiment with. Pretty much all the light comes out the end, and the internal reflection does some odd things, but they did what we needed, for next to nothing, cost wise.

[ImagineerTom]

I used to have to do this back at school (my school was affiliated to a cathedral) and struggled until it was pointed out to me that stained glass windows are designed and made to be lit by sunlight - using a different colour temperature or a different angle of light means you are fighting against everything the original designers and makers spent a lifetime perfecting.

 

Defused light helps but to be honest getting a warm white light source up really high and pointing diagonally downwards through the window is going to make a lot more difference to how it looks than trying to mask and direct a cool white source from the ground. We ended up using garden floodlights winched up flagpoles outside.

[timmeh2]

Hi

 

Depending on how big the windows are, you might get away with IP-rated LED panels.

 

They aren't cheap to buy, but someone might stock them.

 

I have done this, although we used Kino Flo panels hung from a scaff structure built on the outside.

 

Expensive, time-consuming and even then it didn't look right. The post-production guys had a lot of work to do to make it look authentic.

 

All the best

Timmeh

[TomHoward]

Thanks all - to be honest we are 90% there with the floods as they are, but it could be better. It’s only for a one-off talk on the windows which is in the eve so they just need some illumination to be seen.

I haven’t got the means of putting diffusion over the whole windows, but I could diffuse the floods. I tried a stand with the flood more directly outside the window but it made the flood really visible which was a bit of a problem.

I’m on a bit of a power budget as I have 2x 13A sockets to do 8/9 windows so about 6000W total.

 

I’ll keep experimenting, thanks for the pointers

[Jivemaster]

You could illuminate each window in order, as the talk progresses along/across/around the windows. NOT lighting some areas could highlight the areas of interest and save you some current draw.

[MarkPAman]

I once did this for a small chapel in a cemetery with no power available, as the only electric we could find was a lighting circuit. I used a pair of battery powered LED floods from Screwfix. Talk about each window was with inside lights turned off - then they put them on to move to the next, which was my cue to move.

[david.elsbury]

...stained glass windows are designed and made to be lit by sunlight...

 

getting a warm white light source up really high and pointing diagonally downwards through the window is going to make a lot more difference to how it looks than trying to mask and direct a cool white source from the ground. We ended up using garden floodlights winched up flagpoles outside.

but... daylight is a very blue colour source compared to tungsten /warm white.

Wouldn’t that reinforce that a daylight HMI source would be best?

[ImagineerTom]

That was what teenage me was told and did - it’s probably good I didn’t become a lighting person :-p

 

The point about the angle of light is important though. Stained glass is designed to be lit from above and viewed from below; don’t fight that