Anyone who thinks about this for a minute knows: if you want maximum light on a countertop , you place the light directly overhead, or 24 inches off the wall. But that’s not how it’s been taught for the past 3 decades. Two of the most popular texts for kitchen designers have illustrations showing can lights placed 48 to 56 inches off the wall, usually in the walkway between wall cabinets and the island.
For my current ProRemodeler article, “Recessed Lighting Reconsidered” I turned my client’s home into a lighting lab, testing two different size cans, 4 and 5 inches, with 4 types of lamps for each.
How much does the light level fall off as you move the can lights away from the task? Depends on the lamp used. Using the popular Par30 LED flood at 24 inches out, I was able to generate 42.8 foot candles (fc) on the task. Move that light just a foot further to 36 inches out, light level drops to 27. Stand a cook at the countertop, and he/she shadows the light, cutting delivered footcandles to 1.4. Placements further from the counter drop the light level to barely useable levels.
NKBA and IES recommended minimum light levels for work surfaces are 50 foot candles, a value I was only able to achieve with more focused beams, like narrow floods and spots. Perhaps the lighting experts who place the cans so they are little more than ambient light are counting on the undercabinet lights doing the heavy lifting. Good luck with that. See my sidebar in the article titled “Undercabinet Lights Won’t Save You”.
My takeaway from the experiment was that you can’t manage what you don’t measure, so every kitchen designer should at the very least put a light meter app on their Smartphone and start checking what the light levels are on the work surfaces of every kitchen they do. Otherwise, you’re just guessing!