Hello,
@reyalp
thanks for the link, i take a look!

Let's see if I can find a starting point.
@Microfunguy
I try to explain.
DOF is growing with distance. So I use an exponential function to set the focus.
Redundant focus, I would like to leave out.
g=f+(d*(i^5)/(10^5)+i)*10*b
g = next focus
f = current focus
i (i=1 to a) = number off shoot
b = multiple of the step size
d = rise of function
I hope it is understandable.
bye,
Nando