In the previous post, the color noise was tamed by adjusting the color range. The fireworks in yesterday’s image is nice, and easily qualifies as completed art. But that is not the only choice, less fireworks and more emphasis on shape as with today’s image is also a worthy goal.
For today’s image, the linear color scale knob is not enough. The blue in today’s picture, and the sparkly areas of yesterday’s have higher iteration counts than the surrounding area. But the distribution of counts is not uniform. The rate of change is higher in the higher count areas.
A linear scale adjustment can change the overall rate of change, but the relative rate of change between the high and low count areas will remain the same.
The different rate of change is desirable for image composition, it directs focus to where it belongs, it helps the foreground pop out from the background. But how much is the right amount? Of course there is no single answer, it depends on moods and tastes. We need another knob to turn.
So for today’s image, I use the square root of the scale-adjusted iteration count for the color index. The square root function serves to squeeze together the high count values, and reduce the color variation in that area.