A Cry to Abandon Kelvin Ratings (an end to K-Obsession)

[grim]

Why are people so 'K-Obsessed'? Two bulbs that are manufacturer labeled with a certain #K can have very different spectra, and spectra, really, is where it is at.

So when are we going to get to the point when we're looking at spectra versus spectra instead of comparing (or being obsessed with) Kelvin ratings?

(if you haven't been in the computer field for a while, the below will probably make no sense to you)

It's kind of like back in the old computer days when MIPS (# Million Instructions per Second) was king as far as performance measurement went.. Until people realized that MIPS were meaningless, and thus the joke-acronym Meaningless-Indicator-Of-Performance was assigned. Or, maybe now like the gHz assigned to a CPU, where, in reality, there are so many factors that affect performance that gHz really is a meaningless indicator, and in most cases, it is really impossible to compare mHz or gHz values across different CPU architectures, let alone different manufacturers.

So, with that, lets just get off the Kelvin bandwagon here, it's a nice shorthand value to get a very rough idea of the color of a bulb, but, when I see two bulbs with the same Kelvin rating side by side that look radically different, I know the time has come to abandon that measurement and move on.

Unfortunately, there is no easy way to talk about spectrum without a graph or other pictorial (unless you like looking at tables of numbers), and I suppose it is difficult to comprehend for a non-techie, so I guess therein lies the problem.

Everyone knew that 10K was best, well, then 20K was best, then someone found the 6.5K was best, and now well something between 12-15K is best, so is anything really the best, or is nothing the best? Or, well, it is a little more complicated than just looking at the "meaningless-indicator-of-lighting-performance" that the K-Rating has turned into..

Let's be a little smarter and throw the "-K-" into the same trashcan as "watts-per-gallon".

jb

[capncook]

There is nothing wrong with the kelvin rating, its nothing but the color temperature of the light emitted. Its a quantifiable number, used in other fields such as metallugry etc. The REAL problem is people harping about PAR ratings on lamps- par ratings were developed to determine the amount of 'photosynthetically available raidation' for terrestreal plants (ie wide/visible spectrum). Its a problem because plants operate best in the red/green spectrum, wheras corals operate best in the blue (water tends to scatter all red/yellow/orange/green light- at 10m everything looks blue for a reason), so the par rating is a 'totally' usless number. Proof in fact is that 20k radiums have the worst par ratings of all lamps, but experienced sps folks know their corals grow and color up great under these lamps.

Kelvin isnt bad- you know a 20k lamp is going to be really blue, a 10k is going to be totally white, a 6.5k is going to be very yellow, etc. Thats all there is to it. The reason there tends to be fads in lighting is that some people are saying '6.5k has the best par', and 20k guys are saying, 'we have the best color', and everyone else is stuck in between.

...

well, now i must shamelessly plug my new 14k hamilton. :P what a spectacular color.

[grim]

Originally posted by capncook
Kelvin isnt bad- you know a 20k lamp is going to be really blue, a 10k is going to be totally white, a 6.5k is going to be very yellow, etc. Thats all there is to it. The reason there tends to be fads in lighting is that some people are saying '6.5k has the best par', and 20k guys are saying, 'we have the best color', and everyone else is stuck in between.

...

well, now i must shamelessly plug my new 14k hamilton. :P what a spectacular color.

That is exactly what I'm talking about, a useful comparsion quantity, but really, nothing more. By the way, the "14K" bandwagon made me post this.. I was part of the 20k bandwagon (I fell off and am back to 6.5k now), but when I saw the first posts about 14K, I thought to myself, "here we go again!". :) RC is funny that way, there is always some "fad of the month" going on here.. Not to say that 14K is a fad or anything.. :) just that this place usually goes ape over something, then promptly forgets about it when something else comes along.

jb

[harper]

Agreed, PAR is not of much use comparing lamps. It is useful to compare effects of different reflectors or mountings while using the same lamp. To the topic of K…The real problem is manufactures not using it correctly. Ushio has 10,000 K lamps which range from 6k to 11k depending on watt and style (DE SE). Not that every other manufactures doesn’t. In fact many times K varies lamp to lamp in the same product. 20,000 K lamps don’t even have anything to do with 20,000 Kelvin. Then theres the Iwasaki 50,000 K lamp.

When 4,300 K MHs where king the rating meant something. Some of the 5,000 and 6,500 K lamps where on track too. But not many of the 10,000k and better line up very well with black body radiation. As lamps went from 4300 to 6500 they got bluer, so the mentality was then a 20,000 or 50,000 K lamp must be bluer. Not the case. But it really makes no difference. If a manufacture put 100,000 K on a lamp I would fight someone to get the first one. He he. Comes down to 10,000 K is daylight, 20,000K is blue, and anything in between is blue-day. I don’t think manufactures will put 6,500 K on a new lamp anymore even if it is.

That’s why RC rox, you can see what others have to say about the lamp. And people post comparison pictures of different supposed 10,000 K lamps….

These things matter to me for lamps: observations on growth rates, effects on coral color, aesthetics of the tank, price, and reliability of course too. K really just designates which member of a product line one is referring to. Long long ago lost its scientific value.

[RicksReefs]

6500K is daylight.