It is all relative,what is good or fine to you may not be to me.

Proper foc will yield better arrow flight.
Proper will yield better penetration.
Proper arrow flight will be easier to tune.
Proper foc will haveless affect from wind or objects.
Proper foc will fly and tune better with broadheads.
Proper foc will yield better groups,usually.


With all the above stated,ke,fletching,spine,style of shooting ,etc will play a role.If someone has high ke,the arrow will do better imo with lighter foc than someone with low ke,such as I do.


To give a small example.I tested exact arrows and points that were extremely different in weight.I can't remember but close to 300grains difference.The light arrow at 11% foc penetrated BETTER than the heavy arrow with5% foc.As I increased the point weight on the heavy arrow it did better.The light arrow did better at 11% than it did at 7% or 15%.The arrow was identicall because it was the same arrow,just weighted.The weight didn't affect the spine adversly because the arrow was good from 60# to 100#.


For the record,I pass through deer with NO PROBLEMS.(arrow sticks deep in ground)with 380 grain arrows and expandable broadheads.All with a 58# bow at 28 1/2" draw with a wopping 53-56 ft lb's ke.Fix blade broadheads will hit the same@ 40 yards as field points.I stay with 11% when possible because it works best FOR ME.Some may need something slightly different for optimum but most will be fine between 10-15% as EastonStates.Somecan use less and be fine and some will need more (especially traditional guys).


I really don't mean to overstate foc.It is just another way to get the most but 99% will be well served to try to getfrom 10 -15 and not worry about it.


You asked.