The range "sweet spot" is a nominal sight set point that caters for the widest range span for a given target tolerance. It is useful for quick response shooting when there is little time to consider ranging issues as in some 3D shoots, small game hunting and semi-instinctive shots on close moving targets.
The sweet spot is established when the sight line intersects the arrow's ballistic path at two points. The target tolerance determines the peak ballistic path to sight-line height between the two intersection points.
An example of a sweet spot for a 55 lb compound bow and a ±25 mm target tolerance is a sight setting of 15 m. This gives a very useful sweet range span of 5.2 to 17.8 m. For the same target tolerance and a sight setting of 20 m results in a much reduced useful range span of 17.7 to 21.7 m.
Note that the sweep range is determined by the arrow's ballistic path, the sight geometry and the acceptable tolerance, so is likely to be different on each bow.
The archer can extend the sweet range by maintaining a range awareness and aiming a little below the sight point when outside the sweet range. This can extend the sweet range perhaps by 10% each end.
Once bow, sight and arrow details are known to FlyingSticks the sweet spot calculator automatically calculates close range, far range and the sight set point. The result is placed on the range scale tape if enabled. The target tolerance defaults to ±25 mm, but that can easily be changed. Obviously, the greater the acceptable tolerance, the wider the sweet range span.