1st Italy Trip - 2 weeks in September

Congrats on your anniversary! Visiting the prosecco region sounds lovely and unusual. You can take a train from Venice to Conegliano, and hire a tour guide to see the vineyards and prosecco producers. Everywhere else you mentioned is readily accessible by train. Can't go wrong as a photographer in Venice. I suggest not only seeing Venice proper, but also the islands of the lagoon (Burano, Torcello), and the small island across from San Marco with the San Giorgio Maggiore church - you can take the elevator up the bell tower. All the island visits can be done by vaparetto, and you can get a multi-day pass for it.

If you're looking for a day trip out of Venice, Padova is about 1/2 hour away. I would say a do-not-miss there is the Scrovegni Chapel, which requires online reservations.

It's hard to think of a place in Italy that wouldn't be interesting to photograph, so I wouldn't choose just based on that - you'll get great pictures wherever you choose to go. Even Milan, usually derided as not being of interest or beauty, has some great photo potential (like the cemetery, or some of the old parts of churches dating back to the 4th or 5th century AD, or the gargoyles on top of the Duomo).

If you want more of a "slow" trip, and you don't mind not seeing Florence or Rome on this trip, you could fly into Venice and out of Bologna. See Venice for a few days, then the Veneto region (including the prosecco area). Then go to Emilia-Romagna, seeing Padova and/or Verona on the way. In Emilia-Romagna, see Ferrara, Parma, Modena, Ravenna, and/or Bologna. Fly out of Bologna.

Once you leave Venice this will be a relatively tourist-free itinerary (except for Verona), and you should have a great time! For transportation, you can do it all easily by train except for the prosecco area. I don't know anything about this area, but Googling turned up two detailed articles:

http://www.cntraveler.com/stories/2015-07-13/a-guide-to-italy-prosecco-road
http://www.fodors.com/world/europe/italy/experiences/news/wine-lovers-guide-to-italys-prosecco-region-11432

Both Venice (VCE) and Bologna (BLQ) get flight connections from many European airports, and Venice has some nonstop service from JFK, EWR, PHL, and ATL. I'd start in Venice because it's easier to get acclimated and it's a city very set up for visitors; it's also easier to get to BLQ for your early departure, so ending there is much better than ending in Venice.

You should start by looking at Rick's Venice book, but he doesn't cover many of the destinations I listed above, so you'll have to supplement with other books. Look at as many as you can (use your library) - Rough Guide, Lonely Planet, etc. For food, look at Italy For The Gourmet Traveler (very idiosyncratic, but has some great finds, and the author really loves Bologna and Emilia-Romagna and has lots of info about them).

From a photographer prospective, though the area is somewhat large and will take a chunk of your 2 week timeframe, the Dolomites are lesser known to non-photographers but I would say one of the hottest places in the world right now for photography.
You can easily combine a trip to the Dolomites with Venice ; figure 4 nights Venice, 4 nights Dolomites and you would still have time for the other cities you mention.

You would also in this case want a rental car for the Dolomites but obviously not for Venice or Bologna and most any city.