Wow. My brain is tired. I think I need more caffeine. Or maybe a snack. Have you ever set out to search for something you thought was simple but it turned out to be a lot more complicated than you expected? I was going to write something that seemed quite clever half an hour ago but now I’m feeling a little bit lost.
Start at the beginning I guess. In a comment over there I mentioned one of my little pet peeves – that manufacturers of LED bulbs lie about the brightness of those bulbs. For example, I had a catalog from Heartland America (I get tons of catalogs) and noticed this Ultra 60W LED light bulb. First of all, it’s not 60 watts; it’s 4.4 watts but we’re supposed to believe that it gives out the same light as a 60 watt incandescent bulb. But it only has 340 lumens output. I happen to have a package of 13 watt, “60 watt equivalent”, CFLs and they have a light output of 825 lumens. According to this chart a 60 watt incandescent has a light output of 890 lumens. Hmmm… the CFL is close enough I won’t quibble but 340 lumens = 890 lumens? I don’t think so.
What I had planned to say before I started searching is that we need to stop thinking in terms of watts as a measurement of light output. It’s not. It’s a measurement of electricity. But that’s not going to be easy for most people. Lumens is too large a number. So this morning I was thinking, “What about candlepower?” I have no idea how much light equals one candlepower but it sounds pleasant and friendly so I was wondering if it might give us smaller, friendlier numbers so I searched, hoping to find a nice, easy lumens to candlepower conversion chart.
What I found is that it’s not that easy. In fact it’s quite confusing and it makes my brain hurt. It involves (Oh the humanity!) math! It’s not just that it involves math though. Lumens and candlepower do not measure exactly the same thing so it’s not just a matter of direct conversion from one unit to another.
Candlepower is a rating of light output at the source, using English measurements.
Foot-candles are a measurement of light at an illuminated object.
Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate.
Divide the number of lumens you have produced, or are capable of producing, by 12.57 and you get the candlepower equivalent of that light source.
I had forgotten all about foot-candles. Just what I need – another unit of measurement. That’s an entertaining article, by the way, even if it is slightly confusing for the tech challenged or the insufficiently caffeinated. But anyway, now it sort of makes sense how LED bulb manufacturers can get away with saying their bulbs are brighter than they actually are. I also learned that candlepower is obsolete and the new term is “candela” which is okay but I like candlepower better. I say we start a movement to bring back candlepower. We can define it any way we want to. Why not? If LED manufacturers can say 340 lumens is equal to 890 lumens why can’t we pick our own favorite units and define them any way we like?