LED bulbs for garage/shop

Bring along a salt shaker when you're shopping for lights. That "Kelvin rating" stuff is thrown around as if it's this giant, big, massively important thing to the exclusion of all other things. It is not! Use it as a general guideline to know what kind of light you'll get—when a reputable manufacturer says "2700K", that's a yellow-orange-brownish white light like a regular old "soft white" light bulb. "3000K" is a warm (reddish) neutral white. "4000K" is a cool (bluish) neutral white. "5000K" is a cooler (more bluish), and "6000K" is even cooler (way blue). A higher number is not better; these aren't rankings or grades.

The reason why CCT (these kelvin ratings) are trumpeted so loudly is because fluorescent and LED light sources tend to be deficient in terms of another measure that's more important to how well you can see: CRI, Colour Rendering Index, that is how accurately the light source renders colours. Most fluoro and LED light sources are deficient in red, so items that are anything like red-orange-magenta-pink is going to look muddy or "off" (including people).

In itself that's not such a big deal when you're out in the shop working on car parts, but light that's too blue still makes problems. Light colour is a fairly complicated subject, but here are some key points:

Up to a certain intensity, compared to a yellower-white light (lower "kelvin"), a bluer-white light (higher "kelvin") causes about 50% more discomfort glare—WITHOUT any advantage in seeing. That is: given two lights of equal intensity, one producing a warmer-white light (yellower, lower CCT) and one producing a colder-white light (bluer, higher CCT), the warmer-white light will produce significantly less glare.

Above the threshold intensity, other effects come into play: blue and violet are the most difficult colors for the human visual system to process. Blue light scatters within the eye, and focuses ahead of the retina rather than on it. Prove this to yourself easily: next time you're in a window seat on a plane landing at night, take a look at the runway and taxiway lights: the amber, red, and green ones appear in sharp focus, but the deep blue ones look fuzzy. Or find a shopping centre with a storefront sign spelled out in letters lit in deep blue: unless you're at close distance, those letters' edges appear fuzzy, while adjacent signs of other colors don't.

How this matters to work lights, shop lights, street lights, and headlamps: if they're too blue, they create the very uncomfortable sensation of "light that's there, but doesn't work" (i.e., you can see that the light is on, you can see its light falling on the surrounding area, but you still feel like you can't see as well as you should be able to with that amount of light).

There is a small theoretical efficiency advantage to higher-CCT (bluer, colder, higher "kelvin") LEDs, which lets makers print higher output numbers on their packaging (never mind that a pretty large proportion of that bluer output is useless to your eyes) and marketers love babbling about "whiter" light (no, it's not really) and "closer to natural daylight" (no, it's not really), so it's easier to find high-"kelvin" LED lights.

Plus, there's all kinds of bulk wrap flushing around in the consumer lighting market. Not only people slapping whatever "kelvin" numbers they want on whatever light they want (calling a yellow or amber light "3000K", etc) but also this widespread nonsense about so-called "full spectrum" or "broad spectrum" light. Those are bogus terms; they mean whatever the marketer wants you to think they mean at any given moment.