Ok, well you caught us. We do not do a true Square Law in our dimming curves and have not since around 1990. In fact, persons running
ETC dimming next to any other manufacturers dimming can sometimes spot a difference in light output from similar lamps.
Why do we not do Square Law? We, to be frank, critical
lighting designer eyes don't like it. While theoretically Square Law is supposed to give you the desired performance, in reality it does not. Why is this? There are very many reasons and a few have been
identified by JD.
It takes some energy to get a lamp lit and then right after that you then only need to vary
voltage small incremental amounts to then make larger changes in light output. Near the top of the curve, again, small changes in
voltage can create non-proportional outputs in light. All of this is as seen by the human eye, which ultimately was the deciding factor in our implementation. Oh, and the eye is not a perfect responder as well.
So, by the time you add the lamp physics and eye physiology, you get some difference between math and reality. The important
point here is that the curve in our dimmers provide what looks to be a linear light increase as processed by the brain.
In almost all cases, this is why we
call it Mod Sq Law, but I don't remember what a
console set to IES Sq Law may do as we have rarely even used it. The default output on consoles is linear as we rely on the dimmers to apply a curve.
I guess I missed why the OP is trying to map this all out. Is it because he is wanting to get ideal curve performance from the analog dimmers? Note that analog dimmers are suspect to curves set by electrical design,
passive component choices and certainly by the previously mentioned
trim settings. JD is right....done correctly, a very nice bottom end is a joy on some old dimmers. With resistors, and expecially capacitors, aging [assuming these are old analog dimmers], there is likely a good variance from
dimmer to
dimmer. Hence the reason
LMI went to digital dimming in an industry leading move in the 80s.
Well, you can
call me out on any of this that is confusing or you think is wrong. I may not have this all sorted correctly.
You guys are keeping me up late
David
oh, well, I guess it's not too much of a secret that we don't do strict Square Law as it's been on our public documentation for well over a decade...