Convoy wanted a mode group which stopped at half power. It was a request they’ve gotten repeatedly over the years.
There is conflicting research on this.
Going by physics, it should be an x**2 sort of curve. Basically, the inverse square law, same way we calculate candelas. Half the distance is double the brightness, a third of the distance is nine times as bright.
But the human eye doesn’t perceive in a linear fashion, so the closest thing to consensus in the research suggests using a x**3 curve instead. Basically, take the inverse square law and raise its power by one to account for the way humans perceive brightness. That’s the most widely accepted guideline for mode spacing.
Some argue that a logarithmic curve is more appropriate. And, at medium levels, the curves are really close. But it deviates more at the very low end, where a logarithmic method puts modes too close together, and the very high end, where it puts modes too far apart.
I generally adjust the curve based on the individual light and its purpose. For this, I made a ramp calculator to generate the curves, and it allows the user to select any of several different shapes.
On older lights I mostly used x*3. But on some newer, higher-powered lights, I’ve found that a x9 curve works better. This increases the resolution of the lower modes, and makes the high end of the curve steeper, which is desirable on lights which are very overpowered for their size, like the Emisar D4. But for the exact same brightness range on a larger light, I’d probably use x5 or x*3.
So… TL;DR: It depends.
