When I was in Rome in August 2009, there was no pollution to speak of, but we had a couple of sunny days and possibly some wind that may explain that, at least my classic tourist-snaps from the top of St. Peter are smog-free, maybe we were lucky
I have gone trough the photo's I took when I went to Rome and even though I am normally a longer-lens kind of guy, I see that the main part of all the shots I've done, are done with my 17-40 on that trip. Most of the shots are at or below 24mm. (mostly of architecture etc)
Since I only had 2-3 days there (and that the girlfriend at the time came down with an inflammation of the kidney on our way there), we did the very typical tourist-route indeed.
- St. Peter
- Colosseum
- Some walking about in the inner-city (but unfortunately also some time spent in the hospital).
The only times I used a longer focal-length, since I did bring my 70-200 back then, was when taking photos of people (Swiss-guard and others), and the statues and ruins along Via del fori imperiali (the road from
Altare della Patria to the Colosseum) and a few details here and there, and of those, most of them are around 100-125mm.
If you want to get a good panorama of the inner-parts of the Colosseum, 17mm will just cover the whole thing.
To get a good pano of Piazza San Pietro (the area in-front of the St. Peter church), 24mm and below will at least give you some of that. (but I also used 50mm and longer to get a cool effect of all the pillars and all the doves there).
Anyway, I am going to break with convention and tell you to consider your *D* option as well, because inside St. Peter church itself, I was working with ISO's around 1000-1600, I don't have a shot with lesser ISO from there. (but I did use F4 lenses, so if you have faster ones, you
just might be able to drop down to ISO 400,
maybe).
It all depends on your shooting-style, typical number of snaps etc and if you are a mainly film-guy or, like me 50/50 to 70/30 in favor of *D* when I travel.
These days, even if I do bring a *D* setup with me, I make sure to stuff a Leica with a 50mm and a few rolls in the bag too.
- Very few of my shots in Rome were between 50 and 100mm though, I see most were below 40mm and the rest around 100-125mm
I would never bring a battery-grip with any bodies I have, unless I plan to use portrait mode (IE. photo-shoots), since the camera-bulk and weight does increase a lot with them, usually. (I understand you to have a condition that may influence your way to holding the camera, so that is surely up to you).
And don't forget to eat....a lot.....they know food

)))