<a href=showthread.php?s=&postid=9072548#post9072548 target=_blank>Originally posted</a> by TekCat
Maybe this was asked/answered before, if so I appologize for cluttering the thread. But I was wondering, when overdriving 54W T5 with 80W ballast what does it do to spectrum of the bulb? In theory, the higher energy - the higher frequency (lower wavelength). Or am I on drugs again? 
TIA
Yes and no. If you were to look at a graph of the different outputs, the line that represents the different spectrums is the same. If you look at Sanjay's reeflightinginfoarchive.com graphs, its a bit like comparing the same bulb that runs on a Icecap ballast to one on a M80 ballast. The line's curvature stays the same, but with the M80 ballast, the line is a little bit higher.
Technically, that means its the same spectrum then, no?
Well, not really. If you compare the %'ges of different wavelengths, you might find that even though everything was boosted by the same numerical value, adding a PAR value of 5 to 90 isnt as significant as adding that 5 to 5. This is often how it is when you overdrive a bulb. The red spectrum might be non-existant, but you boost its output that little bit and all of a sudden you have a 100% increase in red wavelengths, and only a 5% increase in the blue. Being that with some bulbs like the blue and actinic bulbs, this means that the look can change quite a bit, since if you boost all spectrums in ROY G BIV, and the bulb
normally only makes blue and purple... raising all those other wavelengths, even if they still pale in comparison the the huge blue spike: all together they add up, and in a big way because there will be 100% more red, orange, yellow, and green than there was before, and only 5% more blue, and 10% more purple say.
Its like when you go diving. As you go deeper in the water, the light field graph doesnt change much after 5m...
But as you go deeper, the color changes, right? It gets bluer, no? Well, how could this be? If you look at the red spectrum at 5m, its still barely there, and even though the graph doesnt change much if any, at 10m of depth, that value goes to nil. So even though the graph is the same, the overall appearance is much different... while the blue levels might have decreased by 20-25%, the red was reduced by 100%. This applies much in the same way to overdriving a bulb... except you are raising all values. With some bulbs you luck out, as even with the raised output and line graph, there may still be no values for warmer spectrums with a blue bulb, but this is not the norm. Most bulbs that have a narrow spectrum (which happen to be blue and actinic in this case) end up looking 'whiter' when overdriven. The same would be true if we had a narrow output bulb that made red light... raising its output would increase its bluer spectrums more than red.
