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The Abundance of Choice

I remember the first time I ever bought a car. I don’t mean when dad gave me his second car, but the first one for which I actually laid down my hard earned cash. I did a lot of homework researching my options and doing due diligence. There were so many choices, I was overwhelmed. When I finally made up my mind and signed the purchase contract, I was buzzing with excitement. All my friends were impressed with the car and congratulated me on a fine purchase. For the next few days I was outside in the driveway, washing and waxing, buffing and shining every nook and cranny of that automobile. It felt good.

Then reality set in. I thought about the cost of insurance coverage and I was sure my agent’s price quote has an extra zero in it. Does insurance really cost that much? And when I went to fill up the tank with gas I discovered that my gas bill is going to be almost as much as my car payment. Slowly I began to realize what I failed to realize when I bought the car. Perhaps I could have settled for something other than a foreign sports car.

When it comes to buying automated lighting, there is a lot to know. The decision to buy automated lighting is perhaps the easiest part of the entire transaction. After that, it becomes much more difficult to sort out which lights to buy. The choices are many. There are over four hundred models of automated lighting offered by dozens of manufacturers around the world. Once you decide to buy moving lights you have to choose between moving mirrors and moving yokes, domestic and imports, glass gobos and metal gobos, magnetic power supplies and electronic switching power supplies, and more. You have to decide how much money you can afford to spend, and, most importantly, you have to know how the lighting system you buy will be serviced and maintained properly.

Some of your choices will be dictated by the constraints of the situation, whether it’s the budget, the ceiling height, the size of the sanctuary or room in which the lights are to be installed, or the decisions that others have already made. Without a doubt, the first consideration will be your budget.

The Buck Doesn’t Stop Here
There is more to the cost of automated lighting than meets the eye. The cost of the fixture is only the beginning. The ancillary items that you need to complete a lighting system are the controller, data distribution, power distribution, rigging hardware, installation labor, and programming labor. Then there are other optional items such as custom gobos, custom colors, and alternate lenses. On the back end you have to consider maintenance and operational costs, which include replacement lamps, electricity, labor, spare parts, and freight costs (in the case of outside repairs).

A typical automated lighting system costs… well, name a figure, as long as it’s over $15,000.

$50,000? Yes, you could easily spend that much and more.

$100,000? That’s very common.

$150,000? Probably even more common.

$250,000? It’s been done.

$500,000? Believe it or not, you could put together a state-of-the-art lighting rig with automated lighting and spend this much money. Chances are, you don’t need to. But be aware that an average automated lighting system that includes four fixtures, a controller, data distribution, power distribution, rigging hardware, installation labor, programming labor, and options will cost in the range of about $20,000 to $75,000 or more. So fix a large number in your head before you start shopping, then do your best to work that number down.

But don’t forget about the ongoing maintenance and operation costs. If you buy brand new gear – and I highly recommend that you do – then most of the cost of repairs will be covered for at least one year by the manufacturers warranty. But realize that should anything need repair, most manufacturers warranties do not cover anything except the parts and bench labor. That means that if you have to hire a technician to take the fixture down, rent a man lift to get the technician up to the fixture, or if you have to ship the fixture back to the factory, you are expected to bear those costs. In the best-case scenario, the company that you bought the gear from will handle those tasks at their expense. So it doesn’t always pay to award the sale to the lowest bidder, particularly if they are an out-of-town catalog sales company. Sometimes it pays to pay more attention to the quality of the service instead of the price tag. Make sure you know ahead of time what to expect should one of your lighting instruments need repair (and it will).

A Hundred Dollars per Letter?
After repairs, your next biggest concern will be lamp replacement costs. The majority of the automated fixtures on the market today use discharge lamps instead of incandescent lamps. Discharge lamps are far more efficient than incandescent, but they also cost more. Some of the more common discharge lamp types in automated lighting fixtures are CDM, MSR, HMI, HTI, and MSD lamps. A typical lamp can cost anywhere from $65 to $375 each. For some lamps, that’s about a hundred dollars per letter.

The average lamp life varies quite a bit, typically from 400 hours to 6,000 hours. The most common lamps have an average lamp life of around 750 to 1000 hours. That doesn’t mean that every single lamp you buy will give you that many hours of operation. It means that out of a sample batch, say 100 lamps, half of them will last at least as long as the average life. The other half could fail in as few as 100 hours. But as long as at least half last the average number of hours, then they are considered within tolerance.

The trend in discharge lamps and automated lighting is toward longer life lamps. For many MSR lamps there is a direct MSD long life replacement. They can be retrofitted in any fixture that uses an equivalent MSR lamp with no modification at all. Typically an MSD lamp will have an average lamp life of 2000 hours where the equivalent MSR lamp is around 750 hours. The cost is probably ten percent higher, but the longer life more than makes up for it. The other tradeoff is that the CRI, or the Color Rendering Index is lower in longer life lamps. The CRI is an indicator of how natural a subject will look under the light. The sole exception is the Philips CDM 150, which is a 6,000 average life lamp with a very high CRI of 96.

How Much Light Do You Need?
Once you have an idea of the upper limit of your budget, then you can start to narrow down your options. Regardless of whether you need an entire three-point lighting system for television or video production, or whether you just want to augment your existing lighting system with automated lighting for special effects, you need to establish how much light you need from each instrument. Light output is a function of the lamp source and the optical system in a fixture. It does not always reflect the wattage of the fixture. It’s important to evaluate the luminous flux emanating from the fixture rather than the wattage being consumed by the fixture. Luminous flux is a measure of the light output while wattage is a measure of the energy being consumed by the fixture. The fallacy in looking at the power consumption spec to gauge the light output of the fixture is that every fixture has a great degree of variation in the energy efficiency. Some fixtures produce a lot of light with little power consumption and visa versa. The only true measure of light output is the luminous flux, which is a quantity that is measured in lumens.

Unfortunately, almost every manufacturer of automated lighting uses a different method to convey the light output. Some will give you a raw number in lumens, while others will give you a table or chart showing the illuminance at different throw distances. Still others will give you the luminous intensity in candelas. It’s up to you to be able to translate data back and forth in order to compare two or more fixtures.

Ultimately, the information we are after is how much light a fixture will put on the subject at a certain projection distance. That is the measure of illuminance and it is always measured in footcandles (in the English system) or lux (in the metric system). The easiest method of conveying this information is to give you a table or chart showing the center beam illumination at given throw distances. But that’s not always the case.

Luminous Flux
If you are starting with luminous flux in lumens and you want to know illumination in footcandles at a certain distance, then you have to know several things. First of all, you have to know the beam angle of the fixture and the distance it will have to travel to the target. From that you can calculate (Oh, you went and said the “c” word! You didn’t tell me I was going to have to do MATH! – Yes, there are some actual real-world applications for those seemingly abstract concepts you were supposed to learn in math class. This is an area that is rich in the application of math. Get used to it. Embrace it. Enjoy it!) the area of the beam produced by the fixture.

Area = (radius)2

Radius = throw distance x tan (beam angle x 2)

For example, if the fixture you are looking at has a beam angle of 12 degrees, then it will produce a spot with a radius of 44″ at a distance of 35′.

Radius = 35 x tan (12 x 2) = 35 x tan 6 = 3.68′ = 3′ 8″ = 44″

Area = 3.14 x (3.68′)2

Area = 42.5 square feet

Once you know the area of the beam, you can calculate the illumination at the required distance.

Illumination = luminous flux area (at throw distance)

If, for example, the fixture in the above example has a luminous flux of 8,000 lumens, then we can calculate the illumination as follows.

Illumination = 8,000 lumens 42.5 square feet

Illumination = 188 footcandles

Luminous Intensity
If the specifications give you the luminous intensity in candelas, then all you need to know to calculate the illumination is the throw distance. Using the same example as above, suppose the fixture specifies a luminous intensity of 230,000 candelas. Then we could use the following equation to calculate the illumination.

Illumination = luminous intensity (candelas) x (throw distance)2

Illumination = 230,000 x (35)2

Illumination = 187.8 footcandles

Here’s a hint to help you figure out which of these equations to use. Look at the units of measure. If they are given in lumens, then use the formula with the area. If they are given in candelas, use the formula with the square of the distance.

Beam and Field
You should know that these two equations only tell you the value of the illumination at the center of the beam. It says nothing about the beam profile. The beam profile is a graphical representation of how the illumination falls off from the center of the beam. Some beam profiles are flat and some are very peaked in the center. The ideal beam profile is a cosine distribution, which looks like one half of a cosine wave. The reason that a cosine beam profile is ideal is because two overlapping beams with a cosine distribution produce a perfectly uniform field. That’s because if the two beams overlap at the 50% drop off point then the sum of the illumination levels of the two beams is always 100%.

Uniform illumination is very important, particularly if film or video is involved. The human eye is much more forgiving than the camera, and some variation in light levels is not critical for the live audience. But in video and film production, it is critical. A slight variation in light levels can produce drastic changes on a video monitor.

The point at which the beam illumination drops to 50% of the peak value is called the beam angle. That is a very useful value to know because it gives you the useful angle of two overlapping beams. The point at which the beam drops off to 10% of the peak value is called the field angle.

For example, suppose you have two fixtures with a 16″ field angle and the beam profile is a perfect cosine distribution. Then the beam angle would be 8″ and two overlapping beams would provide 16″ of uniform coverage. At a 36′ throw that would cover about 10′ on the stage. For uniform illumination across a 60′ stage, it would require twelve fixtures. So you can see that the beam angle tells you a lot about how well a group of fixtures can uniformly cover a stage.

Illumination Levels
Once you know how to evaluate the light output of a fixture, you can calculate how much illumination it will produce at a particular throw distance in your own venue. About 100 footcandles for general illumination should produce satisfactory results in most situations. Lower light levels might make it difficult to get good results for video production. Higher light levels serve to draw and keep the attention focused where it should be. People tend to focus toward areas of strong lighting and away from darker areas.

Optical Quality
It’s one thing to have a fixture that produces the quantity of light that you need, but it’s yet another to find a fixture that produces both the quantity and quality of light to meet your needs. All optics are created differently. Some optical designs lend themselves to be more efficient and produce as much light as possible, while others lend themselves to produce sharp image projection at the cost of efficiency. If you are planning to do a lot of image projections, pay close attention to the center to edge focus of the fixture. Find a glass pattern with a lot of fine detail and focus it sharply on the center of the image. Then look at the outer edges of the image and notice how sharp the focus is. If, on the other hand, you are planning to use your lighting only for general illumination and beam work, then the sharpness of the image is less important.

We’ve talked about the cost of a lighting system, lamp replacement cost, and illumination requirements. Beyond that there is a lot to know about features and effects, far too much to cover in the pages of a magazine. Once you find a fixture that is affordable and produces the quantity and quality of light that you need, the rest is more subjective. You should decide which features and effects you must have and which ones you would like to have. For example, the ability to produce moire patterns is a nice effect, but it’s probably not something that might be used a lot in a sanctuary under ordinary circumstances. On the other hand, having two rotating, indexable gobo wheels with glass patterns could be very useful. It’s up to you to decide. That’s the fun part.

Automated lighting is the state-of-the-art in theatrical lighting and it can be fun and exciting. It can provide all the utilitarian functions of conventional theatrical lighting plus a lot more effects that are just not possible to duplicate with conventional lighting. Buying new automated lighting can be a daunting undertaking, but if you arm yourself with information you will have a much better buying experience. Once you have decided to buy automated lighting, do your homework and research all your options. Don’t wait until after you have made your purchase to find out how much it costs to fill up the tank.

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