Almost everywhere in Siena,
there are signs that read
"No flash no tripod."
(While this is moderately irksome,
the signs that read 'no photo' are worse--
and they are in a lot of the shops, too,
because apparently the sellers of knicknacks
don't want people taking home souvenirs unless they pay for them.)
Anyway, thankfully, most places are also fairly well lit,
so I can get moderately decent quality teaching photos.
(One of the things I hate about the 'no photo' policy
is when I see a perfect example of some iconographic scene
and would love to show it to my classes
but cannot take a photo
and of course they don't sell one, because the scene is too obscure,
and even if they did, it would be a poor quality postcard anyway.)
Thankfully, Wikimedia Commons has good files
that can be used for free
on many of the Really Big Stuff
like Duccio's "Maesta" or the Lorenzetti government frescoes.
And I have been able in many museums
to take some good details without flash or tripod.
Here are the Baptistery Font,
a Pieta by Vecchietta
and a detail of the Annunciation from the San Bernardino oratory.