Overcoming Backlighting

[jad17555]

I was asked to try to figure out a solution for a lighting problem at a local church. The sanctuary, which was built in 1994, is a 50' diameter circle in a 3/4 round configuration. with a stained glass window at the back of the stage area. The pastor either stands at the pulpit stage right in front of the American flag of behind the altar in the center. Both are about 2/3 of the way back from the front. They had minimal issues before COVID livestream but now are trying to find a fix that will allow the pastor to be seen against the window. The second picture shows one of 2 sets of 8 fixtures with Par38 Medium Side prong lamps that haven't worked for 20+ years (allegedly a cable was cut while installing a roof). The furthest set of three on the right is about 30 feet away at a 40 degree angle from the Pulpit.

My question: Is it worth it to rewire these lights replacing the lamps with $70-$100 LED floods? or Is there a better way to get Key and Fill light on the pastor so the camera doesn't zone in on the window.

Thanks

 

[TimMc]

I'd be more inclined to treat the offending window. What's the exterior like?

 

[jad17555]

@TimMc It is in the Northwest wall of the building. I am not sure what the outside covering is

 

[FMEng]

Most video cameras have a setting to compensate for backlighting, but the pulpit and altar are in dark holes. The whole platform would benefit from an even wash of light. At that distance, you need spots, not a floods. PAR38 side prong incandescent lamps are rare enough that I doubt there are LED bulbs that would do the job. Scratch using the old fixtures.

The location with a 40 degree angle is good for preventing facial shadows. Getting access and redoing the wiring will be expensive, so you'll want to get this right the first time. Invite your local theatrical lighting dealer in for a recommendation for lights and placement that will look good and last. I see a projection screen, so spill on that needs to be limited. There are stage lights with a hard edge cutoff that would solve that, such at an ETC Source Four LED. The cross could use a spotlight, too.

 

[Searchlight]

Move the camera(s) sideways so the window is out of the shot.

 

[jad17555]

Most video cameras have a setting to compensate for backlighting, but the pulpit and altar are in dark holes. The whole platform would benefit from an even wash of light. At that distance, you need spots, not a floods. PAR38 side prong incandescent lamps are rare enough that I doubt there are LED bulbs that would do the job. Scratch using the old fixtures.

The location with a 40 degree angle is good for preventing facial shadows. Getting access and redoing the wiring will be expensive, so you'll want to get this right the first time. Invite your local theatrical lighting dealer in for a recommendation for lights and placement that will look good and last. I see a projection screen, so spill on that needs to be limited. There are stage lights with a hard edge cutoff that would solve that, such at an ETC Source Four LED. The cross could use a spotlight, too.

Thanks i agree we should get the theater folks involved.. Actually, there is a series of 120W equivalent lamps made by Solais. I installed 32 of them in another church i work with when they first came out about 5 years ago. 31 of them are still working. They come in 15, 25, and 40 degree beam width.

 

[TimMc]

If the stained glass window is to be part of the 'set' for the purpose of the streaming video (in addition to being an architectural feature of the church), it will be helpful if it looks the same every time. It is likely there will be days when there is heavy cloud cover or storms as well as seasonal variations in solar angles in addition to the bright, sun-shiny days.

On bright, summer days: what will this look like when you "paint" the pastor/altar with enough light to overcome the Really Big Moving Light outdoors? Next question is "what fixtures give us the coverage and output needed to make this look good on camera" (and not ridiculous live). followed by "how will we mount, power, and control these fixtures?" What needs to change in the winter, or when the sky is cloudy or overcast?

The window is a beautiful piece that helps "tell the story" of what this particular church is about. Using it effectively probably means having a fair bit of control over how it presents, and THOSE decisions start involving committees...

Suggestion - on a bright, non-Sunday morning take some lights into the room and see how much it will take to make the front light a couple f-stops brighter than the window... If it takes so much front light that the pastor doesn't feel comfortable... or it might take less than I'm edu-guessing it will and the project becomes mostly mounting and power.

 

[theatremgr]

II think that there are several issues needing attention.
The first step in this process would be to actually measure the amount of light present on the scene. The window is a great variable so it needs to be measured at several states of lighting.
Second I would measure the "talent" in various locations.
A very big caution is that LED light is properly rendered by the camera sensors. It would be necessary to photograph the white and black balance before actually installing fixtures.
This work will be very valuable in the final outcome. Measure and then decide.
KEN

 

[seanandkate]

I agree with @TimMc : I would treat the window. Could you mount a curtain rod above and get some custom black sheer curtains / black scrim to pull across on those days when the sun is really bright to knock the backlight down a few f stops? Then when you are filming on dull days, or just not filming, you could pull them aside to let the stained glass shine.

 

[TimMc]

I agree with @TimMc : I would treat the window. Could you mount a curtain rod above and get some custom black sheer curtains / black scrim to pull across on those days when the sun is really bright to knock the backlight down a few f stops? Then when you are filming on dull days, or just not filming, you could pull them aside to let the stained glass shine.

I was considering suggestion of an indoor scrim, 18% gray, so it would take color/front light or even some projection... but that gets into the 'committee' thing.

 

[theatremgr]

I have an assignment where there is daylight filter through stained glass windows, LED light and incandescent light all in the same scenes.
Perhaps you might look at this single camera video of a virtual church service to see our implementation.

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Thanks for looking
KEN

 

[Ben Stiegler]

Another approach to the window is to use a motorized roll-down fabric that can be light-reducing, without totally blocking it. I do this regularly on a smaller scale with motorized shades, and often we put a dual roller mechanism up that allows for 1 or both drops to be lowered. Thus you could stack a 10% transparent fabric and a 5% and have 3 different levels of opacity available. What's the width there? sometimes we need to gang together multiple rollers to cover wider spans. Glad to chat with you about it - catch me at [email protected]

 

[jad17555]

Thanks for all of the replies. The expertise available on this listserv is amazing.

 

[Craig Hauber]

I was considering suggestion of an indoor scrim, 18% gray, so it would take color/front light or even some projection... but that gets into the 'committee' thing.

The last facility I had to deal with exactly this type of situation we just put neutral-density gel in front of the glass to demo -without telling anyone in the "committee"
It worked so well nobody could tell.
Until a committee meeting one day they dropped one strip just to show the contrast -after recovering from their sudden blinding, there was unanimous approval.
There was a bit of reflection from the gel itself so they had a contractor remove the outside clear panes and insert the gel between that and the stained glass to restore the original "texture" of the inner stained-glass surface.

A few years later they were back to the same problem as the solar UV had bleached-out the ND pigment significantly so they had the actual glass tinted with storefront-grade coatings.

I do not remember the ND percentage or vendor, (decades ago now) but it was sourced by people in the photography industry and not stage lighting. Also wasn't cheap, but far less than removing the commercial-grade double-pane glazing on the outside for something that initially was just a concept test.