Mixed Fields of Visibility

Trying to figure out how to handle realistic fields of visibility when there are open areas and forested areas on my map.  Blocking fields of view through the forested areas from the open areas is easy.    But when the players move into forested areas is there an easy way to drop the visibility distance down to a Realistic level without going in and resetting it for each player individually?

Other than putting a ridiculous number of tokens (and associated DL paths) (which is also not a perfect way to show this) I don't think there is really a way without using the API (something like the darkness closing in example script).

Standard Fog of War is probably your best bet.