“Introduction to Lighting Theory” or “Bright Shop Design”

Okay. I won’t call the pre-existing wiring lighting and wiring job in my shop, before the demolition/renovation that got it to where it is today, shoddy. But just remember that if you don’t say some things, doesn’t mean it isn’t true. Upon entering the building, half the lights didn’t work, those that did flickered and hummed. The wiring was a hazard, it was strewn everywhere, nailed-through in places and many pieces of rubber cladding were missing. Some duplex boxes didn’t work, there were light switches that didn’t attach to anything, and wiring that went no where. Some plugs were walled over, there were lengths of cable with no connection on either end. Many times two lengths of cable were attached with nothing more than mar connectors, or to make matters even more exciting, just black electrical tape. Needless to say I tore the hell out of it all as soon as I could. At present, the room is a little more dark and dreary, but only 2 out of 8 circuits are now used with marginal difference in the functionality of the shop. Terrifying. I’ve devoted many hours (I’m sure too many, if you asked Sarah) to shop lighting theory and design, and I’ve learned quite a bit. I’d like to share some of that with you today.

My method worked beautifully for me, as did the path I took to discovering it. I will present you with some step-by-step methods to shop design that may help clarify some of the confusion and … (wait for it)… shed some light on the situation. OH! See what I did there? Clever.

1. Determine Desired CRI, Lighting Intensity, Temperature

Many authorities will recommend many different brightnesses for a veritable cornucopia of environments. I’ll share with you some of the basic environments that some people may actually find familiar. So far as I can, I refer to the authorities in the specific sector to which I am referring. I could talk to a Physics PhD, but I would likely get much more information than I need and much of it will be out of context. Sources like this helped me a great deal to gather some context for my problem: Wood Magazine.

I’m going to use LUX (lumens per square meter) rather than FootCandles (candellas per square foot), because the base-10 conversions are much cleaner once all dimensions are converted into meters, rather than feet and inches.

CRI (Colour Rendering Index) basically means, at what accuracy will the colours be seen as their true colour as seen in direct sunlight. The noonday summers sun has a CRI of 100, while varying lightbulbs have varying CRI’s. The closer to 100, the more real it looks, but remember that if you build/colour something under 100 CRI lamps, it will look different in a darkened living room with 60 CRI lamps. I prefer to go for ~100 CRI photo realism and take my chances, it’s easier on the eyes anyway, but we all have our preferences. Rule of thumb, the higher the better.

Lighting Intensity: Just how much brightness per given area is present? Twilight offers less brightness than does noontime, and kitchens are usually brighter than living rooms. This link from AutoDesk (proud makers of the AutoCAD family of drafting products, I’m a huge fan) has many tables that assist in this thread. Feel free to browse it for supplemental information

  • It explains that Full Daylight offers 10,752 of brightness upon the earth, and that twilight offers 10.8.
  • It goes on to explain that Cable tunnels, nighttime sidewalk, parking lots have a LUX of approximately 50, and is described as Interiors rarely used for visual tasks (no perception of detail). Not what we want for our workshop.
  • Libraries, sports and assembly halls, teaching spaces, lecture theaters ought to have 300 LUX, that offers us some safe context.
  • Detailed electronics assembly, drafting, cabinet making, supermarkets requires 1000 LUX. Sounds about right.
  • On the other hand it explains that Hand tailoring, precision assembly, detailed drafting, assembly of minute mechanisms would require approximately 1500 -2000 LUX, and summarizes conditions of Interior with demand for maximum visual acuity (low contrast, optical aids & local lighting will be of advantage). I’m an extremist, but I don’t need to bleach my wood by the brightness of my shop.

1000-1500 LUX (100-150 foot candles) seems about right for my application, as well it could be for yours.

Temperature: Try not to think of how hot the light will be, or how much energy from the circuit will be converted into heat, but think of how hotter fires burn white, and cooler fires burn orange. Ever see a “warm” light bulb or a “cool” light bulb? Consider how something looks under a match flame or a torch (1700k temperature), it kinda washes everything in orange hue. Great for a fireplace, but not for a workshop. What about typical, unfrosted incandescent lamps (3000k)? Those cool white bulbs (5000k)? The harsh brightness of a white screen on an LDC (10,000k)? You might not think so, but 5000k is known as “daylight frequency” and is one of the closest synthetic colour temperatures to daylight, which is actually closer to 6500k, but that temperature is not always easy to synthesis efficiently. Fluorescent light tubes are readily available in the 5000k temperature spectrum, and make it much easier to work in a shop when the light is closer to natural sunlight. Think of it as tricking your body to thinking it’s outside during a sunset.

VERDICT: CRI 90 to 100, 1000 LUX intensity and 5000k temperature bulbs. With me so far? Great 🙂

2. Building Dimensions to Determine System Demand

Remember that I’ll reverse my methods for this, because the metric system is a little cleaner for the math.

In my case, my building is approximately 10m Long by 6m wide by 3.5m high (32′ long x 20′ wide by 11′ high). This will give us an area that needs to be illuminated of 60m (~800 sqft) and a distance from bulbs to floor of 3.5m (~11 ft).

So; in order to get 1000 LUX (lumens per square meter) we need only do a little math: (Intensity) x (Area) = (1000 LUX) x (60 sq.m.) = 60,000 lumens are required to light up that area. The fact that the building is 11′ high as opposes to a typical 8′ doesn’t matter a whole lot. LUX is based upon the distance, sure, but an extra meter in a sealed room is a little different than 100m with a flashlight. There IS a difference, but what difference it is seems to be relatively insignificant when using whole light fixtures as a unit of increment. Moving on.

VERDICT: We need 60,000 Lumens of light from the entire system in order to brighten the whole building to 1000LUX; appropriate for cabinetry, as it happens!

3. Choose Your Lighting Products/Technology

I am partial to Fluorescent light tubes. By swapping out the magnetic ballast (the little black box inside) with an electronic one, the hum and flicker is erased, making it function a normal light, and they are able to start up at MUCH colder temperatures. The 5000k bulbs with 90 CRI are available at many building supply stores, and they last for years and years without replacing. Seems to be a no-brainer for me!

I happen to like light that is very, very well distributed. One huge spotlight in the middle of your shop may seem like a good idea at the time, using less cabling and so on, but you’d cast hideous shadows across your whole building. More point-sources of light the better. Don’t forget that you need task-lighting for individual tasks like grinding, routing, honing, etc. These are just general-purpose lighting so you won’t stub your toes and able to do general work everywhere.

I happen to like the 4′ double-tube light fixtures. They only cost about $40.00, the replacement ballasts cost about $20.00 and the two-pack of bulbs/tubes might run you another $30.00. SO, in a nut shell, for $100.00 per unit, you’ve got a wicked-bright, long-lasting, fire-and-forget light source that fires off as much as 3000 lumens per tube, and there’s two of those per fixture. Not bad!

So now we’re talkin’ $100.00 per light at 6000 lumens per fixture. Yeah? We need 60,000 lumens to light my shop floor, so we only need 10 lights. Drop a cool grand on the lighting demand and you’ve got the situation well under control. Also, insofar as wiring, each fixture now eats up 64 watts (2x32W), and there’s ten of these. In North America and our 110vAC services, that’s only 640W / 110vAC = 5.8 amps on the circuit. I’ve never seen a fuse/breaker that small. It’s easy enough to wire those 10 lights to a single fuse/breaker and have a couple of different light switches control half the bank each. So if you’re just sweeping the floors or if you leave lights on at night, you needn’t eat up a full 5kWhrs (demand for the whole circuit) per 8-hour day needlessly. It adds up.

Assuming you’re not all bored to death already, I’ll do a quick recap.

1. Determine Desired CRI, Lighting Intensity, Temperature
VERDICT: CRI 90 to 100, 1000 LUX intensity and 5000k temperature bulbs.

2. Building Dimensions to Determine System Demand
VERDICT: We need 60,000 Lumens of light

3. Choose Your Lighting Products/Technology
10 units of 4′ double-tube (32W ea) Fluorescent lights, at about $100.00 each

But how did I get there?

(Lux = Lumens / meter)… We want to know the lumens, so algrebra gets us this ( Lumens = Lux * Meter )
Lumens = 1000 * 60 = 60,000 lumens.

Double-tube fixtures, at 3000 lumens per tube means 6000 lumens per fixture: (# of Fixtures = Needed Lumens / Fixture lumens)
# Fixtures = 60000 / 6000 = 10 Fixtures.

$100.00 a piece is a $1,000.00 lighting array, of 10 lamps on the ceiling providing 1000 LUX to the floor.

That’s all I did to determine my lighting intensity. I’m going to go with 16 lights in my ceiling, spread across 4 switches. That’s just personal preference, because when my father or neighbors visit, I cannot count on their eyes being as young and sensitive to contrast as mine. Besides, I’d rather do overkill and adjust my lighting needs with the extra switches controlling 4 lights each.

(Remember our desired light intensity for Cabinetry is 1000 LUX [lumens per square meter]
and the desired light intensity for ultra-fine small-parts work is much more)

1 Switch; 400 LUX (4 lights)
2 Switches: 800 LUX (8 lights)
3 Switches: 1200 LUX (12 lights)
4 Switches: 1600 LUX (16 lights)

Each of us must adapt our own system to our own needs. What I may also do is stagger the switches. No need having four parallel rows of brightness. I may figure out a different way to help disperse the light better. Maybe the first switch can light the four corners. A second can do 4 lights evenly around the perimeter, the third can do the other perimeter lights and the last one can light all four lights in the center. That makes a huge degree of adaptability to the lighting array, and can act as task-lighting in a pinch. You only want to spend money on buying power to have light where you need it. Why have the wood storage room lights tied into your main bank?

Be smart, be efficient, be thoughtful when you design anything that costs you money to operate. You needn’t spent the time getting the equivalent of a Bachelor of Science Minor in Physics, and be able to teach a college course in Lighting Theory to be able to set up your own lights in your own shop, but remember that if you pay someone to do the work, they could do exactly what you tell them to, perhaps knowing it’s a terrible idea, or they could try to fleece you for all you’re worth to make a buck. There are folks in between, but not enough of them.

This is my contribution to you being a wise consumer, and my effort to brighten your day. Enjoy 🙂

Oh! Some closing thoughts before I go; on lighting theory that doesn’t directly involve your lights!

Walls: Painting walls white will go a long way towards helping prevent dark spots and helping the light bounce around your building. Smoother-textured walls, rather than rough textures like stucco, will do the same. The closer to mirrors, obviously, the better the walls will reflect your energy

Windows: Having windows is a great source of natural light, but it is highly variable. Overcast days, different points throughout the day, measure of clarity OF your windows (dust, grease, paint, grime, etc) all effect how much light they provide. For my shop, I’m doing away with all the glass, boarding them over and insulating the cavities. I would rather pay a little extra for overhead lighting at noon than to have to deal with moving light when I’m working on a long project, or recording DIY Youtube videos in variable lighting conditions.

Storage: You might not believe it, but open shelves will swallow large amounts of light. Having smooth, white, opaque cupboard doors on all storage locations will increase the efficiency of light reflection down towards your floor. Why waste luminosity brightening up your lumber racks if you’re not using them? Open the door and let the light bask your boards on an as-needed basis.

Deflectors: You can buy curved reflective panels for your lights. What is the sense in having a light shine a full 180 degree angle around the light (When roof mounted) when you need the energy on the floor where you are? In my case, with such a high ceiling, I could use a narrow deflector than an 8′ ceiling. These deflectors will darken the ceiling a little bit, but there will always be light energy reaching up there, by reflecting off the floor and walls. We want as much focused on the floor as we can, and deflectors can help.

Cleaning Maintenance: The dust and sticky particulate matter in a woodworking/finishing shop can be intense; even with superior dust collection. There is no reason to believe that no dust/crud will cling to the diffusers (the plastic shields that make the light spread more evenly distributed), walls, floors or any supplemental light deflectors. Brightening up the floor, walls, ceilings with a fresh coat of light-coloured paint can go a long way, and can also help smooth-out the surface, making it more reflective. Cleaning the bugs and dirt out of the light fixtures can also go a long way. Cleanliness may be next to godliness, but it also adds to brightness!


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