A summary thread on lighting

[DTEguy]

Originally Posted by Ray

A HO T5 bulb, on the other hand, with a 6400°K color temperature, puts out about 100 and 90, respectively.

Is this roughly a universal PAR level for all 6400K-6700K T5HO tubes? Thanks...

[Andre]

I have a 8 bulb t5 fixture with 4 foot 54 watt full spectrum tubes. How close is too close (other than overheating plants), how far should I place my Catts. If they are very close (5 inches) do I only get the benefit of two or three of the tubes versus the benefit of all 8 tubes. I grow Catt. walkerianas, and nobiliors. They are not booming but some of them have a suntan. Tubes are on for 13-14 hours.

[Ray]

Originally Posted by DTEguy

Is this roughly a universal PAR level for all 6400K-6700K T5HO tubes? Thanks...

No.

First of all PAR is the sum of the photons emitted between 400 & 700 nm.

Second, the color temperature is a descriptor of the spectrum, not the intensity of it.

And lastly, a fluorescent tube is not a black body radiator, so the "corrected" color temperature is meant to fool the eye - not the plant - into thinking it is looking at a black body radiator. If you get a decent plant light bulb, the chances of the spectrum being better for the plant improve, but again, that says nothing about the intensity of light emitted, or the actual spectral wavelengths.

---------- Post added at 11:25 AM ---------- Previous post was at 11:22 AM ----------

Originally Posted by Andre

I have a 8 bulb t5 fixture with 4 foot 54 watt full spectrum tubes. How close is too close (other than overheating plants), how far should I place my Catts. If they are very close (5 inches) do I only get the benefit of two or three of the tubes versus the benefit of all 8 tubes. I grow Catt. walkerianas, and nobiliors. They are not booming but some of them have a suntan. Tubes are on for 13-14 hours.

Sounds to me like you're overdoing it.

8 tubes x 54 watts x 90 lumens/watt = 38,800 lumens. I'd bet you could back that off to 18" or more with no issues, but you really should measure to be certain.

[DTEguy]

Please let me rephrase my question.

When you said 100 and 90 energy units for Blue and red for 6400K T5HO, is this a common feature for all T5HO at 6400k to have a balanced blue and red output? Or are you referring to a specific brand which you read or measured?

Thanks.

[Ray]

No, I am not referring to any specific brand, nor am I saying that it is universally true.

If you look at the absorption spectrum of chlorophyll, you will find that the red peak at roughly 660nm is roughly 90% of the height of the blue one at 430nm.

A 6400°K black body radiator will also have that same intensity ratio of those wavelengths, but will also have greater intensity in-between.

A plant light that is rated at 6400°K corrected color temperature is likely to have emissions at those wavelengths that match those ratios reasonably well, while a 6400°K CCT fluorescent not made for plants may not.

[estación seca]

This thread hasn't been updated in a long time. Plants' light requirements have not changed, but technology has changed a lot since 2013. If you're contemplating buying grow lights, look at newer threads in this forum for more up-to-date information on equipment. The information here on what plants need is still good.

[WaterWitchin]

Originally Posted by estación seca

This thread hasn't been updated in a long time. Plants' light requirements have not changed, but technology has changed a lot since 2013. If you're contemplating buying grow lights, look at newer threads in this forum for more up-to-date information on equipment. The information here on what plants need is still good.

I'd never looked at this sticky, but I agree with you ES. I'm going to unstick it, as the information is outdated. And to someone newer coming along who wants to learn, it's not helpful overall. Thanks for pointing it out.

If someone knowledgeable about lights and lighting wants to step up to the plate and give a synopsis of present knowledge and technology, that would be grand.

[Steve83]

I'm pretty familiar with, and have grown under a variety of lights (cfl, t5, led, hid).

Its really down to led vs hid at this point. Even among leds, you have cob, board style units, strips (great for shelves), conversions etc. The biggest issues with many led lamps (it isn't rocket science to build one), are that they are not driven to the wattage specified ie. claims to be 200w, but draws much less when measured.

[Steve83]

I should have also elaborated, that I am working on a write-up reagrding my trials and tribulations with hid growing in a tent.

But could also do a separate piece covering led and hid lighting, and recommendations for layout.