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Confused about light spectrum

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Hello all, new poster here.

Long story short, I've been reading about Kelvin temperature and the actual range of spectrum of light for CFL and fluorescent bulbs, and it seems the two aren't necessarily related to one another? I want to experiment with different bulbs but I'm having trouble deciding which factors I should consider more. Can I just go to the hardware store and pick up any bulbs that meet my wattage requirements for my particular application, or do I need a bulb that is specific to growing plants?

Sorry if this seems like a dumb question, but I keep reading conflicting information regarding Kelvin and spectrum. I read that any 5000 to 6500k bulbs should be fine, and then I read that the bulb needs to meet certain spectrum requirements for reds, greens, and blues to be truly effective. I also see bulbs that are 2700k and labeled as aquarium/plant bulbs.

Thanks!
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and it seems the two aren't necessarily related to one another?
The relationship is "loose"..
K temp (w/ fluorescent it is more correctly CCT) is a spectral summation to produce a given color temp. As such adding and subtracting various colors of the spectrum can still lead to the same SUM..
Third sort of "variable" is CCT.. which defines how close colors will match to a certain standard..

Gets confusing..

The CCT rating for a lamp, luminaire, or fixture is a general indication of its color appearance (warm or cool). Light sources with a CCT rating below 3200K are usually classified as "warm", while those with a CCT rating above 4000K are usually classified as "cool" in appearance. Although CCT is a good indication of the lamp's general appearance, it does not provide information about the lamp’s spectral power distribution. For example, as shown in Figure 4, two lamps A and B can have the same CCT (6000K) but different color appearance. Lamp A appears greenish white while Lamp B appears pinkish [1].
https://www.google.com/url?sa=t&rct...fDI5L3f3g&sig2=_qN8mIRCrGL19Im6ZQ6NxA&cad=rja

what is the goal of your experiments??

Last point is spectrum is the only true "picture" of a light..
If you want to do "color" experiments I suggest using DIY LED's..
 

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Discussion Starter · #3 ·
My goal is to just get a bulb that is pleasing to the eye as far as color goes, but to have the required spectrum to grow low to medium light plants. I here about people buying off the shelf bulbs from Walmart/Home depot/Lowe's that don't have any kind of spectrum charts or information and just using those. Are they just lucky with their choice or should I be looking for something that has an actual chart to back up my needs?
 

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My goal is to just get a bulb that is pleasing to the eye as far as color goes, but to have the required spectrum to grow low to medium light plants. I here about people buying off the shelf bulbs from Walmart/Home depot/Lowe's that don't have any kind of spectrum charts or information and just using those. Are they just lucky with their choice or should I be looking for something that has an actual chart to back up my needs?
most of the success is due to quantity, not quality.. Plants will adapt to most any spectrum.. "pleasing to the eye as far as color goes" is subjective and has nothing to do w/ plants per se..
CRI is a rough approx. to "pleasing" in lights above 5000k.. It means colors are real and well distributed (baseline it is judged against is 6500k daylight ).

So if you want "pleasing" and good growth.. pick high CRI bulbs in a power that suits your tank..
80CRI or better.. preferably in the 90's..
Then # of photons one needs..

e.g.. grows plants great.. looks like............




Technically the 2 issues are sort of separate..


And you have to decide what is "pleasing" to you.. Some like crisp blue/white.. others more earthy yellow/green
 

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Discussion Starter · #5 ·
So wattage and placement are more important? I'm probably overthinking this, but I should be able to pick up a 15w T8 6500k fluorescent bulb and be okay for the most part? It's for a 10 gallon low tech tank with low light plants like java fern, various anubias ect.

I have another 5 gallon tank That I will be growing the same thing, but want to use a CFL bulb hanging over the tank and want to be sure I can pick up a 6500k ish bulb with 10 to 20 watts and be in the general ballpark for lighting.
 

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So wattage and placement are more important? I'm probably overthinking this, but I should be able to pick up a 15w T8 6500k fluorescent bulb and be okay for the most part? It's for a 10 gallon low tech tank with low light plants like java fern, various anubias ect.

I have another 5 gallon tank That I will be growing the same thing, but want to use a CFL bulb hanging over the tank and want to be sure I can pick up a 6500k ish bulb with 10 to 20 watts and be in the general ballpark for lighting.
Yes and no. Light distribution is certainly important, you'll want uniform distribution.

Regarding wattage and spectrum and plants... Think of it as having some gallon buckets in a parking lot. You can get a fire hose and spray water all about knowing you will put some water in the buckets or you can get a small hose and connect each bucket. One is more precise and uses less power to grow the plants but looks bad. The other look better and brighter because some of the energy is wasted on esthetics.

The values you give should be enough or even too much for the project you describe, even if you use common bulbs
 
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