I am still a little unclear on why with the 1X going to 2X, we need to increase FEC by one stop AND decrease EC by 1/2 to 2/3 stops, it feels like a double compensation.
Let me write it out and the penny may drop;
Taking EC down would under expose the image, both ambient and flash, by the 1/2 to 2/3 stop, so putting in +1 FEC brings that up element up again and gives the desired ratio, hmmm. I think I get it
The key (I think) is it did this maintaining the same exposure for the brightest element.
However, when I started thinking about it, taking the table at face value, it seemed that just increasing FEC by +1 would do it, but I guess this would over-expose the flash lit elements.
Not withstanding that, the ratio still felt right at 2X what it was.
I think I'm being a silly billy - it may just be me being thick
, or maybe this rambling will help you understand my mis-understanding and clarify it for all (I hope).
Or maybe this is the difference in the two methods of expressing the ratios you were talking about.