Stage Light v Projection Lumens

[zachzaba]

Hi everyone!
I'm an LD that mainly uses LEDs for my rig and I'm trying to accommodate a projectionist at an upcoming show so they can bring something with enough fire power. This is when the question of how many lumens my stage is actually putting out came up. I understand that this is a "fluid" measurement so my best guess would be to go full white and intensity just to establish the top of my output threshold (of course during a show I may never reach that point). I've performed this exercise in the past with an incandescent rig but not surprising the world of LED specs is a bit of a rabbit hole.

Our stage has 5 fixture types that I rotate out for different shows that include beams, spots, b-eyes and pars; currently have either lumen or lux specs for all of them. My question I guess is with the Lux formula (Lux=lumen/ft2). I can "visualize" this on a surface or screen but how does it work for a crowd or camera...what would the ft2 part of formula be? If I was at FOH with the projectionist would it just be our area? For a camera is the square footage just that of the device, so extremely small? I'm sure I've severely overthought this but once I sat down and actually thought about it the head scratching began. Thanks!

 

[dbaxter]

Our experience with projections is that it has more to do with how your normal stage lights are aimed than how many lumens they have. No projector is going to overpower (show up) a SourceFour aimed at the same surface. We've done many musicals with the dancers lit from a higher angle so that the back wall stays dark enough for the projection.

 

[zachzaba]

Thanks for the response. I guess in my world most of my upstage fixtures are pointed out so the camera would need to see through these lights to view what is projected.

 

[jtweigandt]

Yep. nothing directly illuminating the surface that you are projecting to. Usually have to design around projections
I'm a rank make it up as you go along amatuer, so take that at it's face value. Also think of the relative amount of "lightfield"
entering the observer's eye from the projection vs everything else. Review how Copperfield vanished the statue of Liberty and you can see
it's all relative.. backscatter, foreground, background, and subject lighting all in balance.

 

[Jay Ashworth]

I'm the projection guy in my theatre, and my boss is the LD, and yes, it's more about "don't hit the screen" than almost anything else... though you will find that bounce and spill are imporant considerations.

Short version: make sure your V1 is ready to project the appropriate images when your LD is designing, so he can adjust as necessary.

If you're working to a screen flown from a lineset (rather than, say, your cyc), and it's not backed, then this problem gets much, much worse.

That said, we just replaced a 5kl Eiki with a 10kl Panasonic laser, and the difference is night and damn day; easily 3 times as bright, maybe 2 full stops, and that's best-case vs full-cyc. Hoping the Super Bowl happens. ;-}

 

[jtweigandt]

Heres an example during design phase for "39 Steps" at a local Barn Theater. Back projected scrim .. ended up bouncing off a mirror to double my throw length.
You can see the foreground is quite bright here. The projector is just a 2000 lumen Viewsonic projector. I even had a flight simulator animated biplane sequence with Actors on stools pantomiming the Aerial attack.

 

[jtweigandt]

Veering slightly off but has anyone used "stacked" projectors. Some of the epsons brag that they are set up to do this nicely now.

 

[RonHebbard]

Thanks for the response. I guess in my world most of my upstage fixtures are pointed out so the camera would need to see through these lights to view what is projected.

Cross lighting performers from both wings can work well if you fire across parallel to your projection surface and lose your light between legs on the far side rather than having it illuminate and / or bounce / reflect off of any surfaces.
Consider lighting from side booms, either floor standing or tailed down from flown LX pipes.
Toodleoo!
Ron Hebbard