Colour temperature and CRI get all the attention, and they matter. But the question that stalls more projects than any other is simpler than that. How bright does this actually need to be?
It’s a fair question, and the answer isn’t printed on the box. A spec sheet gives you lumens per metre in a laboratory. What you care about is how much light lands on the product once it has passed through a diffuser, travelled a certain distance and hit a surface that may absorb most of it. Those two numbers can be a long way apart.
Here’s how we work through it with customers.
Colour temperature and CRI get all the attention, and they matter. But the question that stalls more projects than any other is simpler than that. How bright does this actually need to be?
It’s a fair question, and the answer isn’t printed on the box. A spec sheet gives you lumens per metre in a laboratory. What you care about is how much light lands on the product once it has passed through a diffuser, travelled a certain distance and hit a surface that may absorb most of it. Those two numbers can be a long way apart.
Here’s how we work through it with customers.
Watts Tell You Cost, Lumens Tell You Light
Plenty of strip lighting is still sold on watts per metre, which is a habit left over from incandescent lamps. Watts tell you what a run will draw and what size driver it needs. They tell you nothing reliable about output, because efficacy varies enormously between a budget strip and a quality one.
Compare lumens per metre instead, and if you’re comparing two products, check lumens per watt as well. That figure is the honest measure of how good the LEDs are.
As a rough guide across quality strip:
Low output at around 8 to 10 watts per metre delivers roughly 700 to 900 lumens per metre. Good for subtle cove work and shelf accents.
Mid output at around 14 watts per metre delivers roughly 1,200 to 1,500 lumens per metre. This is the workhorse for display cabinets and joinery.
High output at 20 watts per metre and above delivers 1,800 lumens per metre or more. Reserved for signage, deep cabinets and anywhere daylight is competing.
Start With The Surface, Not The Strip
The useful target isn’t lumens at all. It’s lux, which is lumens landing on a square metre of the thing you’re lighting.
For general retail floor and circulation, 300 to 500 lux is normal. Feature displays and shelving typically want 750 to 1,000 lux so they read as brighter than their surroundings. Jewellery, cosmetics and anything where fine detail sells the product often needs 1,000 lux or more. Ambient cove lighting sits far lower, often 100 to 200 lux, because its job is atmosphere rather than task light. Chilled food cabinets usually land between 500 and 1,000 lux depending on depth.
The important part is contrast. A display only looks bright if it’s noticeably brighter than what surrounds it, generally by a factor of three or more. Lifting the whole room instead is how retailers end up with an expensive, flat, tiring space. We went through this in more detail in our guide on choosing the right CRI for retail and food displays, where the same principle applies to colour.
Budget For What The Diffuser Takes
This is where paper calculations come unstuck. A clear cover costs you very little, perhaps five percent. A frosted cover takes 10 to 20 percent. A deep opal diffuser, the one that gives you that clean unbroken line of light, can take 25 to 40 percent.
That’s a fair trade, because opal is what makes a run look professional rather than like a strip of dots stuck under a shelf. You just have to allow for it. If you need 800 lux on the shelf through an opal diffuser, specify as though you need well over 1,000.
Distance compounds it. Double the gap between the strip and the surface and you land roughly a quarter of the light. A metre of strip under a 300mm shelf is doing very different work to the same metre lighting a 1.2 metre deep cabinet.
Density Decides Whether It Looks Good
Brightness and quality are separate problems. Density, meaning how many LEDs sit in each metre, governs whether the light reads as a smooth line or a row of hotspots.
At 60 LEDs per metre you’ll see individual dots unless you have real mounting depth behind a good diffuser. At 120 per metre the light evens out at sensible distances. At 240 per metre, or with COB strip where the chips are encapsulated in a continuous emitting line, you get an unbroken glow even in shallow joinery.
The practical rule we use is this. The shallower the recess, the higher the density needs to be. If there’s less than 15mm between the strip and the diffuser, go COB or high density and don’t argue with it. Fitting the strip inside a properly matched channel from our LED profile range gives you that depth and keeps the line straight at the same time.
Strip Or Bar? The Answer Changes The Maths
For joinery, curves and continuous runs, LED strip lighting gives you the flexibility to follow the detail.
For cabinets, chillers and food counters, a rigid bar is often the better tool. Our EcoFresh LED light bars are built for display work, with the optics and mounting sorted so the output goes onto the product rather than into the customer’s eyes. Because they’re a fixed length with a known output, the calculation gets much simpler.
Test It Before You Commit
Specs get you close. The final call should be made on the actual product, in the actual cabinet. Packaging, glass, stainless benchtops and dark timber all change the result, sometimes dramatically.
Order a sample metre, mount it roughly where it will live, and look at it with the merchandise in place. If it looks slightly too bright at that stage, it’s usually about right once the diffuser and the shop’s ambient light are in play.
If you’d rather not guess at any of it, our team offers commercial lighting design and will work the numbers through with you. Give us a call and tell us what you’re lighting.
