how many lumens Does a Work Light have to have? How many lights Do I need in a shop? Where do I put the lights?
Every feel like you are working in a dungeon? Are you squinting and struggling using glorified flash lights that are passed off as "work lights"?
If you are squinting and struggling, get a real work light!
Below I apply basic principles of lighting engineering to show that you why we've made our lights up to 14 times brighter than competitive work lights. Based on this science, you will be able to see that work lights need to be very, very bright to do the job.
How much Light? For over 114 years, starting with the invention of the electric light bulb, the Illuminating Engineering Society (IES) has been dedicated to quantifying lighting quality and promoting good lighting practices. Over all those years nearly every conceivable type of work task has been examined to determine what the recommended light level should be.
Their recommendations are based on the fineness of the seeing task The idea is simple. When it's dim, your eye's pupil expands to gather in more light. But this additional light that's let in the eye is not as tightly focused so that finer details can not be seen well. Conversely, when the workspace is bright, your eye's pupil constricts, and your vision sharpens. Below to the right I provide a chart of recommended light levels measured in foot candles (fc).
Most work light applications fall into 4 broad categories described below:
4 Categories of Work Light Applications
High Intensity Task Lighting
High Intensity Work Bench Lighting
Temporary Area Lighting including Illumination of Vertical Walls
General Shop Lighting
High Intensity Task Lighting
As show in the spread sheet to the right , difficult work requires very high light levels: 100 to 300 foort-candles ( fc). Light levels of 100 or more foot-candles are normally generated with supplemental task work lights. In many areas, like under car hoods, under equipment, in dark attics, and crawlspaces you have to entirely depend upon a bright work light to get the necessary illumination.
Underneath the chart to the right I give you a crude formula that you can use to determine how much illumination work lights provide.
For an example, let's look at auto repair, a task with a recommended illumination of 50 fc. Here car hoods are problematic as they block overhead light fixtures. The formula, shows that our 11 way work light gives you 88 foot Candles 3 feet under our light. But from the same location you only get 15 foot candles of light from the shown 845 lumen under hood light as shown below.
fc=C x lumens of light ; where d is the feet to the light
12.6 d x d
C=1, if light comes off all sides of the fixture
C=2, if light comes off one side of the fixture
C=8, If the light has concentrating lens
The formula over estimates light levels by 10% to 25% if the fixture is about as long as it is far from the work piece.
But, it also ignores light that might be off target, bounce around a room, return, and hit the targeted work surface
High Intensity Work Bench Lighting
If you need to light up a work bench or inspect for flaws, we have the lights for you. 100 fc is a good work bench light level. If the Light fixture is 5 feet above the bench, our "6 tube", 13200 lumen fixture gives 84 fc of direct illumination according to our formula in the previous section. If the light is next to a white wall, you will pick up some indirect illumination from light bouncing off the white wall. And If the rest of the work space is well lit, some light will scatter on your bench from adjacent fixtures too. So our "6 tube "equivalent is a good choice. I You need to mount the lights higher than 5' above the bench, our 22000 lumen "10 tube" equivalent, fixture does 84 fc when mounted 6.5 feet' above the bench.
You want to illuminate all sides of what your are working on. Otherwise you can get shadows. One solution is to use our 4' shop lights tipped inwards as shown in the photo to the upper right where we are illuminating the sides of a statue, just like the one you are carving in your shop right now.
For exacting inspections and very difficult work, 300 fc is the recommended light level.. That's about 1/3rd of the light present outside on an overcast day. Example tasks requiring 300 fc including spot cleaning clothes at a dry cleaner, precision manual welding, fine grinding or manual crafting, cutting clothes, fine assembly or any type of exacting inspection.
It is problematic achieving 300 fc because it's difficult getting enough LEDs in a Single Fixture. So a solution is to cross aim the fixtures so that 2 or more lights are aimed at the same surface as shown In the diagram to the right.
Temporary Area Lighting including Illumination of Vertical Walls
Sometimes, it's nice to just brightly light up the entire room you are working in.
If you are painting, you want all the walls illuminated. The dim lights typically installed in residences, just aren't bright enough to do the job. You need good lighting to see if you are getting good paint coverage with an even coat and no transparent spots.
Likewise during construction, much of the action is occurring in walls and ceilings because that's where wires, pipes, and ducts are run. So you need to both light up the ceiling cavity and provide good vertical foot candles on the walls.
The IES recommended light levels for ordinary painting is 20 foot-candles. This isn't a very high light level. However, you have to illuminate the entire surface area of the room. So that takes a lot of lumens. This is good to know because, many of today's high priced area lights are only powerful enough to light up a closet. And that's only if that light is running at full power.
Here I show the average number of foot candles you should expect on ceilings, floors, and walls for given light fixtures outputs. The first table is a room with virgin sheet rock or light covered paint. The second table is for an unfinished room with no sheetrock.
For information on how these values were calculated and how you can do it yourself I provide this link:
General Shop Lighting
In the previous sections, I discussed high intensity workbench and task lighting. You really need powerful lights to get enough light for many common workshop tasks. The formula that I give in the task lighting section is a starting point to get the light that you need on target for difficult tasks or for areas where overhead lighting is blocked-- e.g. underneath equipment or under a car hood.
However, many times you need to have high light levels all over a shop. Or sometimes, really intense light is only needed at a particular work station and lower light levels are acceptable elsewhere. But you need to know how many lights are required for that lower light level.
So how many of our High Output Shop Lights/Side Lights does it take to illuminate an entire shop?
The IES (Illuminating Engineering Society) recommended light levels for most shop work is 75 to 100 foot candles. The total number of lumens required using this fixture can be approximated by:
Lumens Required = 1.4 x Foot Candles Required x Floor Area (square feet)
You can divide the lumens required by the lumens per fixture (13200 lms for our 6 tube equivalent) to the get the number of fixtures you need.
This formula is good for a 8 to 10 foot ceiling in a rectangular room with white walls and ceilings. You can call or write for exact calculations, otherwise, you can apply increase or decrease the fixture count using the following approximations.:
-30% for a square room,
+15% for non white walls
+30% rectangular room, high ceiling.
+0% square room, high ceiling.
The toughest portion of a room to light is around it’s perimeter. Fewer fixtures in the center of the work space than around the edges. I usually place lights on the walls, down low, pointing into the center of the shop while directly illuminating work benches. And I put lights directly above important pieces of equipment to prevent shadowing.
Here is a layout for a typical two bay repair shop with garage doors on the left end :
Need a Shop Light or Work Bench Light? >>
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