Is there a difference bet 5400k and 5700k???

[Davo]

Gday,

I have finally found a supplier of 55w CF bulbs & ballast's over here in Australia.

I have ordered 5 x reflectors for my setup from AH Supply and when I receive them I will let you know how they perform.

Unfortuantly I can only get 5400k or 5600k bulbs over here in Australia at the moment.

The 5400k bulbs cost $AU14 each and the 5600k cost $23 each over here.

Is it worth the extra expense for the extra 200k for the 5600k?

Dave.
Sydney
Australia

[m.lemay]

If you could look at them running, pick the one that seems less yellow or green and the one that seems brightest. Hopefully the brightest one will also be the whitest. White-bluish-violet are the best for growing plants. If you can't see them running I would pick the une with the highest lumens.

Marcel

[Guttboy]

Ok now my question arises marcel.....

I thought you could not tell the spectrum of a bulb by the visible light it shows to human eyes....2La sent me a link on this...and I am still a bit confused but let me let you see this....

Mike


http://w1.864.telia.com/~u86438141/index.htm

Go to the area about lighting spectrum.....

Having a strong background in the sciences on my end I need some sort of way to determine spectrum...if it is not published then I assume you would have to get out a spectrophotometer or a prism that could measure the refracted light to determine what areas are the highest peaks....this is my GREATEST beef with the WPG rule...and that rule does not take into consideration height above (plant, substrate, etc)....

Anyhow just me babbling again....

[anonapersona]

Oh, a prism! Now that'a cool idea.

[Guttboy]

heheh i have one left over from when i was a kid and my dad was explaining light......its gotta be 20 years old or so....lol

mike

[m.lemay]

Mike: this whole lighting thing is so convoluted. :lol: I really don't want to get into a discussion on the science, I'll leave that to people with spectrographs and prisms. If I were a plant I'd tell you exactly what I prefer but I'll have to settle for pearling as my guide.

The info above was merely based on my experience and visible evidence from my plants. All else being equal, I'd go for the brighter ones. :P

Marcel

[Buck]

You would notice no significant difference over 200k and neither will your plants.

And yes the depth of your tank does have an effect on the wpg rule.... that rule is just to get ya "in the ballpark" and is by no means science.

[2la]

Ask the manufacturer for the spectrum. That's the only way to tell which bulb is 'better' for growing plants. Subjective brightness doesn't really tell you anything. Remember that our eyes are more sensitive to light emitted in the green area of the spectrum, so any bulb with a large spike in the greens is going to appear brighter to us than a similar bulb without a spike there. As an example, a cool white bulb won't grow plants worth a hill of beans despite appearing very bright to our eyes (owing to the heavy emphasis on the green part of the spectrum) compared to a ZooMed Flora*Sun, even though the latter appears dimmer. However, keep in mind that when you're talking about a compact fluorescent, the margin of benefit between one bulb and the other probably is not all that significant at the wattage you're dealing with. Unless the spectra are markedly different, go with whichever one you feel shows off your tank's colors the best.

Mike, I'll give you another example:

Let's say you wanted a bulb that glowed green, say at 3000K (making up a number). You're given two bulbs. The first one has just one phosphor that radiates (i.e., has a spike) in the green area of the spectrum. Boom! You've got a green bulb radiating at 3000K, right? But the second bulb has two phosphors, one that radiates in the yellow area of the spectrum and one that radiates in the blue area of the spectrum. Yellow + blue = green. Boom! You've got another 3000K bulb! How do you determine the spectra when both bulbs appear the same? You can't: That's the point I've been trying to make about predicting the spectrum from the color temperature rating. Of course, real-world physics doesn't quite work out as cleanly as it does in this hypothetical example, but hopefully you get the picture.

[Guttboy]

2la thanks for the explanation that clears a bit of it up. Marcel...I agree with you the plants have to be the judge of the light. I have 2x19wattx6500K bulbs I got from Home Depot (compact flourescent screw ins)...they are very whiteish...I also have 2 25wattx3000 bulbs designed to replace incandescent ones. We shall see which ones work out. I have 2 x 23 watt bulbs coming from 1000bulbs.com to replace the 19 watt ones....we again shall see how they work out.

Mike