The original question:
“I’m wondering what you folks generally recommend for footcandles at any given target area? Over the many years I’ve sold spots, I’ve found 150-200fc to be adequate, but I’ve come to the realization that I never asked you who make the spots what your thoughts are.”
Followspots are great add-on items for shows. However some of the more prevalent questions buyers have is how many lumens or footcandles do I need in order to highlight the talent from afar?
Here’s what we’ve tallied so far and I welcome you to join the discussion.
Per Steve Lerman @ Lycian:
“That’s a great question. My thoughts are this- In order to highlight the performer(s), the followspot must illuminate them in excess of the surrounding lit stage.
On a dark stage any light on a performer would suffice but when was the last time a performance occurred in the dark?
I’m not certain there is a numbers rule but the followspot must out-muscle all the stage lighting because sets and scenery are secondary and color will often be used to set moods while followspots are what draws us to the performer. (Along with a great performance)
Generally, the more professional the show, the more powerful the followspot, again to cut through stage lights.
Little Johnny’s 5th grade talent show will often get by with a low power incandescent followspot because relative to a few pars it suffices.
That may not answer your question but it’s all relative and application specific.
Per Shawn Harmon @ Canto USA:
This is actually one of my favorite discussions lately. I love how you had a formula and now, like so many other folks, you are having to revaluate [sic]. We are too by the way. So back when we were in a world where Front of House was 15 to 50 Source4s or 360Qs or some combo of zoom products that didn’t really do much that 150fc to 200fc was probably correct and a real safe bet for just about every show. Now days we have a much more diverse and intense offering FoH. Some of the movers are in the 20,000 to 30,000 lumen range and the LEDs are shifting that color temp makes that 5600K is not so piercing visually to the stage. To answer this question I need to ask questions. How far away are the follow spot from the stage? What regular fixtures do you have FoH? What does the end-user think is the “normal” foot candle level at plaster line center? Are there movers and LEDs FoH? With this I walk through what they need. If they have 15 to 50 Source 4s and its 150fc in a good bright cue I tell them 150fc is fine. The follow spot is double the surrounding area in intensity and that should be fine. If they have 50 source4s and 12- 30,000 lumen movers doing areas and 30 LEDs for color and faces and they think the stage is 300fc then I say buy as bright as you can afford because a 2:1 contrast ratio is still not going to give them the punch or the look of punch they will need at 300fc. Which makes it complicated. This is also where I say “can I come do a demo?” At the demo I talk about what they want to accomplish. I don’t think I gave you an answer as much as I gave you the start to a formula. Please feel free to keep this thought train going or come see us at the booth at LDI. I’d love to have you take on this approach. If I have one sound bite answer this its, there is no magic answer.
I mostly look for 100 – 150fc at the back of the stage area.
It’s also worth noting that perception science says a truely [sic] attention-getting accent is 10X the surrounding level. On many stages that could mean >500fc!