My partner is driving me up a wall with “No one thinks about kelvins, just buy the 40W!” and I’m over here trying to explain why I’m taking time picking bulbs in a certain Kelvin range and figuring out the needed lumens for a room.
Bonus points for a simple diagram or a true (emphasis on 5) explanation I can link to her.
Cheers!
In: Technology
Buy a smart bulb and you can directly show them the difference in color temperature and intensity. Not a lot to say otherwise.
Temperature = what it looks like, watts = how much power it uses, lumens = how much light you get.
You could go into *why* color temperature is that way and what black body radiation is but I don’t imagine that’s going to be helpful in picking out bulbs.
Lumens/watts are two ways of measuring brightness. If you want more light, you want more lumens. But too much can be unpleasantly bright.
Temperature measures color. Lower numbers are more yellow like an old light bulb and higher numbers are more blue like the sun. People have different preferences, and mismatched temperatures are very noticeable, so people like them to match across a room.
“Kelvins” refers to the color of light it puts out. Scientists have observed that while hot things glow red, really REALLY hot things glow blue; and so they decided to put this same temperature scale on light bulbs to communicate whether a light is more red/yellow in its color, or blue. You can tell what color a light source is by holding a white piece of paper in its shadow. If you do this outside in the sun, the white paper should appear to have a bluish tint in the shadows.
Blue light tends to keep people awake and more alert, can be more “harsh”, and blends well with natural sunlight. Yellow light tends to be softer, “warmer” and more inviting, and easier on the eyes at night.
Kelvin or color temperature is the color on a yellow to blue scale (2800K is very yellow almost orange, 3200-3400 is kinda yellow but it is what we are used to for lighting inside a house is at night, 5000k is daylight whiteish but bluer than what we’re used to in the house, 6500k or anything higher is very blue compared to what we’re used to in a house).
Watts or Lumens are more related to brightness. Lumens is actual brigtheness. Wattage is equivalent to how bright a similar old school tungsten bulb would have been. 60w tungsten (pretty standard) was around 900 lumens. 40w tungsten was around 600lm (more often what is used in ovens and maybe bathroom fixtures with multiple lights). 75w or 1200ish lumen was a brighter indoor bulb if you needed something more than 60w.
I am with you on all this. The wrong light temp (Kelvins) drives me crazy and brightness definitely matters in different situations
“Lumens” are how much *actual output* a lightbulb has: the amount of light shining out of them. “Watts” are how much *power* a lightbulb actually consumes.
The problem is, *when all bulbs were incandescent,* you could just compare power to power, because there weren’t any meaningful differences in efficiency. This is NOT true with LEDs. LED bulbs are dramatically more efficient, that’s kind of the point, and as a result “40W” *does not* mean the same amount of light output from two different LED bulbs. The actual unit that measures light-output is lumens, not watts. Two bulbs that both draw 40W can produce *very* different amounts of light depending on how efficient they are (the more efficient they are, the brighter they will be for a fixed power draw; or, conversely, a more-efficient bulb will draw less power for the same amount of light output.)
Likewise, incandescent bulbs meant for home use were essentially always in exactly the same color temperature range, so of course nobody cared–there weren’t any *choices.* Now, however, we CAN choose the color temperature–and it turns out that color temperature matters for things like helping people sleep better and avoid headaches and fatigue.
Getting the right lightbulb for your needs *can* be worthwhile. Of course, spending a dozen hours getting the *perfect* lightbulb, as opposed to one that is merely *quite good,* may not be an efficient use of time–but looking at least a little is definitely better than just pretending that they’re all the same and grabbing the first thing that comes up.
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