That is a good explanation, Michael.
I am not doing macro but yesterday I made a graph based on my earler post.
The vertical scale is 'relative EV" to indicate change in camera settings for example f/ (by taking log-base2 of the change in luminance [cd/m^2]
Graph is for a 65mm long flash tube.
It also shows that after the distance is further than 2~ 3 times the length of the flash tube, the Gauss Law (inverse square)
is quite accurate.
Closer than that, the EV settings do not change so much.
American taxpayer money at work. I spent almost 24 months in technical schools in the US Navy learning that, plus a million other things.
Originally Posted by wombat2go