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ok i understand that 6400k and 6500k is the color temp. what i want to know is the difference in color detectable to the eye? also which one is better? does it even make a difference?
6400k or 6500k??????
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Yeah, the trouble is these Kelvin numbers are all kind of bogus. Flourescent & MH bulbs don't have a smooth enough spectrum for the Kelvin value to be measurable. Basically the manufactuers just make up a number based on the market they're selling into. With only a 100K difference, it's about equally likely that one is better than the other.
The other problem is "better" is a highly subjective term. What matters is how it looks to you... and it's a safe bet you will see a difference. Lacking any other information, I would go with the bulb with the higher color rendition index (CRI).
If you're lucky you might also find some data on photosynthetic efficiency. For example: http://www.aquabotanic.com/lightcompare.htm
With all due respect to Casey & 125G's, I don't know how they could have an opinion of an unidentified bulb. If you could identify the bulbs, maybe people here can relate some personal experience.
The other problem is "better" is a highly subjective term. What matters is how it looks to you... and it's a safe bet you will see a difference. Lacking any other information, I would go with the bulb with the higher color rendition index (CRI).
If you're lucky you might also find some data on photosynthetic efficiency. For example: http://www.aquabotanic.com/lightcompare.htm
With all due respect to Casey & 125G's, I don't know how they could have an opinion of an unidentified bulb. If you could identify the bulbs, maybe people here can relate some personal experience.
Maybe it's just me, but I think SAT that you agreed with Casey and I and chose the higher CRI or did I not read your post correctly?
elgordoinavw, SAT has a point in that not knowing the manufacturer (and type, PC, NO, VHO or MH) of the bulb makes it a little difficult to give a more specific response. While there may not be much difference between a 64k and 65k bulb on the surface, manufacturer, PAR, spectrum and other bulb characteristics can make a huge difference in what bulb you choose. Given a bulbs spectrum tends to decay over time, a higher CRI is the more desirable amongst hobbyists, the theory being that more life can be had from the bulb. (Some just like the blue color on the other hand). One more thing to think about, a 65k Iwasaki bulb has more blue spectrum to it than many 10k bulbs, but yet does not carry the blue hue that they do. Strange, but that's how it works and supports SAT's arguement that kelvins as a unit of measure can be misleading.
The short answer is that we need more information on the bulbs in question to better assist you.
elgordoinavw, SAT has a point in that not knowing the manufacturer (and type, PC, NO, VHO or MH) of the bulb makes it a little difficult to give a more specific response. While there may not be much difference between a 64k and 65k bulb on the surface, manufacturer, PAR, spectrum and other bulb characteristics can make a huge difference in what bulb you choose. Given a bulbs spectrum tends to decay over time, a higher CRI is the more desirable amongst hobbyists, the theory being that more life can be had from the bulb. (Some just like the blue color on the other hand). One more thing to think about, a 65k Iwasaki bulb has more blue spectrum to it than many 10k bulbs, but yet does not carry the blue hue that they do. Strange, but that's how it works and supports SAT's arguement that kelvins as a unit of measure can be misleading.
The short answer is that we need more information on the bulbs in question to better assist you.
I think 6400 and 6500 k shouldn't make a difference to the eye (in theory).
I would check the brands, and ask here on the board what most experienced people think. If you get cheap bulbs, that I would be concerned about. Many people claim that bulbs with same wattage and same temperature, but different brands will give you slightly different tints of, for example, green, on 6500 Ks.
Provide information as to how would you like your tank to look, what corals you plan to keep, etc.
My 2 cents
I would check the brands, and ask here on the board what most experienced people think. If you get cheap bulbs, that I would be concerned about. Many people claim that bulbs with same wattage and same temperature, but different brands will give you slightly different tints of, for example, green, on 6500 Ks.
Provide information as to how would you like your tank to look, what corals you plan to keep, etc.
My 2 cents
Well, not exactly.125G's said:Maybe it's just me, but I think SAT that you agreed with Casey and I and chose the higher CRI or did I not read your post correctly?
CRI is on a scale of 100, where 100 would be a perfect perceptual match for a radiating black body at the indicated color temperature (Kelvin). The sun has a CRI of 100 at a color temperature of about 5500K (add in the blue sky and daylight averages about 6500K). Incandescent bulbs also have a high CRI, but at about 3000K. Typical flourescent lamps are in the 70s, but a few are in the 90s. I think the Iwasaki 6500K is in the upper 90s, which makes it the closest to natural daylight of any bulb on the market.I think most reefers prefer a color temperature in the 10,000-20,000K range, which appears bluer than the "daylight" bulbs in the 5000-6500K range. You can achieve that by using a high-Kelvin bulb or by supplementing with actinic lamps.
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I dont agree with Sat either I dont like 10k and most of my reef buddies dont either we all run 65k which is closest to natural daylight ,We have some light experts on here they can boggle your mind with there light knowledge.It really depends on the brand and what you like some like blue some dont .
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158 Posts
o.k this is starting to get really technical, all i wanted to know was on the bayco light they have 6500k, but it's hard to get a replacement without paying alot (alot to me is over ten when i can get the same thing at target/hd/lighting store for less), what i wanted to now is would you pay $3.79 for a 6400k 13 watt, or pay the $4.99 for a bayco 6500k replacement bulb? i'm sorry if i didn't specify.
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158 Posts
thanks casey
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