I was wondering what you guys do when you are to shoot, let's say, waterfall or taking photos when its drizzling, misty or foggy and you see what water drops on your lens filter. Do you clean it when you are outside? What do you keep in your bag for cleaning?
I carry several lens cloths that I have accumulated over the years and some tissues as well. I clean water as soon as possible very carefully.
Soft plastic square or rectangular filters (has nobody heard of glass?) will get scratched no matter how much care you take. I like to start with the bulb blower for dust, then a soft brush. But wet stuff requires a wipe with a cloth.