Like someone mentioned, that bright sun is no joke. Over the years, I have found a circular polarizer to be more useful than a basic UV. It cuts through atmospheric haze and makes the water pop. I usually run a B+W 39mm Master Circular Polarizer MRC Nano on my Cron. It provides about 1.5 stops of light reduction, basically acting as a light ND filter anyway. Best of both worlds.

I've had some bad luck with cheap filters causing nasty ghosting lately, which is super frustrating. Unfortunately, many budget options just aren't as good as expected when you're shooting into the sun.

• Hoya 39mm HD3 UV Filter: Pro is the hardened glass, con is it looks a bit plain.
• Leica E39 UVa II Filter: Pro is the perfect match, con is the price. Safety first... I'd hate to see that glass get scratched.

Honestly, since you are heading to the Amalfi Coast, you really need to be careful with that new glass. Salt air and spray can be brutal on lens coatings, and since a Summicron costs several thousand dollars, I would suggest making a high-quality UV filter your top priority. Most people who complain about flare are using cheap glass. If you get something like the B+W 39mm 010 UV-Haze MRC Nano you wont see any degradation in image quality, and it provides that essential physical barrier. It might be a bit pricey at around $60, but it is basically essential for peace of mind. Since the M10 only goes up to a 1/4000s shutter speed, you will definitely blow out your highlights in the midday Italian sun if you try to shoot wide open at f/2. To stay within your $200 budget, you might want to consider also picking up a Hoya 39mm PROND 8 Filter 3-Stop which usually runs about $50. This gives you the flexibility to keep that shallow depth of field without overexposing everything. Make sure to buy the 39mm size specifically for that 35mm Summicron model. I would suggest keeping the UV on 24/7 for protection and just swapping to the ND when the light gets too intense... you definitely dont want to risk a scratch on your very first trip.

Building on the earlier suggestion, salt air is a concern but dont overlook the exposure limits of the M10 shutter. In the bright Italian sun, youll be stuck at f/11 without help. Over the years, I have found a high-quality ND more essential for that wide-open look.

• Use a 3-stop (0.9) ND.
• Stick with brass mounts like those from B+W. The B+W 39mm Master MRC Nano 803 ND 0.9 is basically perfect. It stays sharp without shifting colors.