Automated Fixtures How to calculate light requirement for a live event.

[lightsupergeek]

Hi, I would like to know how lighting engineers and designers figure out how many lighting fixtures are required to lighting up a stage using conventional or automated lights. I have heard of lighting guys who do the calculation based on photometric data of lights they are using for a show. Even I can understand the photometric data. But how bright is bright enough for a stage performance. For example, a Robe 575 AT wash with 12 Degree beam angle at a distance of 10 meters will have an output of 5600 Lux. Now my question is, what is the bench standard Lux value which is good and bright enough for a fashion show. I want to know how the veterans in lighting industry do these calculations.

 

[JD]

Balance is far more important then actual light level. The human eye can accommodate a black to white ratio of almost one million to one. Start with you on stage design. If you are using video projection then the projector's output will probably set the baseline. How bright will the house lights be? If they are on (sometimes the case at fashion shows) then you need to have some level of pop above that to draw attention to the stage. How high is the ceiling? If it is a low ceiling event then you are limited by how much low angle light is going to be hitting the faces of those on stage. There is no such thing as "we need x amount of foot-candles on stage." If it is being filmed or videotaped, there are some limitations there and you should consult the firm handling that.

 

[lightsupergeek]

Thank you very much John, I will get back to you with few more questions later. i am super busy with events.

 

[jmcgowantech]

I'll second what JD said. The only time I encounter a show requiring specific foot candles are symphonies. A lot of them require a minimum of 80 foot candles. The requirement is to set a minimum for the musicians to read the music. A lot of what goes into fixture selection and fixture quantity is based on the event and location. I've run several different types of venues over the years. I re-hash the process every time. What's the event? Is it a fashion show, wedding, concert, etc? A Fashion show will have different needs then a rock show.

Now specifically for a fashion show, you are going to have several different needs.
1st and most important is the look on the run way. It needs to be bright and clean. Minimal shadows. I would light it from multiple directions. Front, back, sides, above, and below. This will need to be the brightest part of the design. I would recommend conventionals such as parcans or source 4 pars. You want to make sure everyone can see the items being modeled but the models can still see where they are going. You can also use strip lights along the run way to wash away some of the shadows created by the downward angled lights.
2nd will be atmosphere. This is where movers and such come into play. You want to make sure the room looks just as classy or hip as the models while not detracting from the models.
3rd general lighting. This mainly applies to converted spaces or arena type venues where the facility lighting doesn't fit your needs. As JD stated, the facility lights are a factor. You may consider leaving them off and handling the utility need of the space on your own. If so, you want to make sure the walk ways are well defined and illuminated. You can use movers or Lekos with shudders to frame these up. You also want to add some general over head lighting to the audience sections of the space. This will serve for finding seating as well as looking at programs. People will want to reference which line is being modeled and by which designer. They will be announced but people either forget or aren't paying attention.

A lot of the actual fixture decision making comes down to what you have personally used in the past and budget.

As to the question, how bright should it be? That's tougher to answer in the sense of numbers. I use the standard of "does it hurt my eyes to look at?" If the answer is yes, its too bright. Its a lot of trial and error when it comes to setting levels. At the end of the day, its up to the client. Set a look. Ask how they feel the level is. Adjust accordingly. Remember, you can always take the intensity down. You can't always add more fixtures day of. Over spec the rig. I've run shows where I hung a typically 120k rig and only use half of it. But I would rather have the option and not need it then need it and not have it.

Side note: I would avoid LEDs on the runway for fashion shows. Depending on the quality of the led it can do weird things to cameras and they will be taking pictures.

I'm not sure if this answers your question or not but that's my 2 cents. Feel free to hit me up with any further questions.

 

[MikeJ]

Video/photography-centric events sometimes do dictate exact photometric. 100fc used to be the standard for Video. Realistically, with newer and much better camera sensors, 60-80 will be plenty, but this will depend on who you are dealing with. This gets pretty particular when you have to balance stage lighting with Video wall or projection, that will be in the shot, or even as the background of the shot. Same goes for balancing say a light cyc behind people on stage.
I have definitely run at about 60fc front light to match a 40k projector as a background on a pretty large screen. I have also just had the video guys turn down the video wall to balance the shot. It's more about ratio than a hard number. You have to match/balance everything to you least bright element.

Even lighting, with maybe 10% variation in level is key for video. Fresnels are probably the best fixtures for getting an even wash. It can be done with pars and some diffusion, but is more time-consuming. Though on that point, look at pretty much every pro boxing and MMA fight, it's an even wash of pars light from 4 sides. Imagine that the Boxing Ring is a checkerboard, each square is light from each side. Same goes for a runway, matching fixture from each side/front side angle, to evenly light and kill shadows.

As far as "you can always turn it down" is pretty much not acceptable using dimmers. Amber shift in tungsten fixtures will become a real problem with white balance after about 10-15%. ND filters and scrims are best practices when it comes to conventionals. But even flooding out one fresnel to make it "dimmer" can work. You can also just turn off a few fixtures completely if you have too much light. Movers usually have mechanical dimmers and are easy to match output. There are lots of LED fixtures now that are great for this type of lighting, but you do have to be selective; some older or cheaper ones do suck on video or photos.