The x*y notation means “x to the power of y”. So, x2 is x squared, x*3 is x cubed, and so on. The “3x the previous mode” shape is a logarithm base 3 with the number of modes chosen to hit a specific ratio.
For example, nine evenly-spaced levels from 0.1 lm to 1000 lm, using a few different curve shapes…
|
x**2
|
x**3
|
x**5
|
x**9
|
log 3
|
|
0.1
|
0.1
|
0.1
|
0.1
|
0.1
|
|
18
|
4.5
|
1.3
|
0.6
|
0.3
|
|
66
|
23
|
6.9
|
2.8
|
1.0
|
|
145
|
66
|
24
|
10
|
3.1
|
|
255
|
143
|
65
|
31
|
10
|
|
395
|
265
|
150
|
84
|
31
|
|
566
|
442
|
307
|
208
|
100
|
|
768
|
684
|
574
|
472
|
316
|
|
1000
|
1000
|
1000
|
1000
|
1000
|
For a light like this, I would probably go with fewer modes and a curve from one of the middle columns. For example, six modes with a x**5 shape it would be: 0.1, 3.8, 30, 128, 398, 1000.