I am from Lucca, Tuscany, also a landscape photographer.
You can go freely in the fields, just have your boots if come now as we got a lot of rain, the owners have nothing against their fields beig shot!.
Also very interesting area for photography is the area in Orciano, Santa Luce and Pieve di Santa Luce, north of Val d'Orcia, just on the Est of Pisa, right in the back of Pisa, watching from the sea.
Lucca itself is a very nice town for pictures.
I will post some pictures taken on Orciano and Santa Luce, if...am able to post a picture, neved did before in the forum!