I have a shoot for a documentary interview on Saturday in Central Park, New York(the park might be loud). Should I mic the subjects with lavs or should a shotgun mic be used? Wouldn't the shotgun capture the noise around them also?
That probably depends if you are shooting this solo or with an audio person. An audio person could be very successful booming something like a Sennheiser 416 and keeping it close enough to minimize other noise. If there's time, you could also put a lav on the person and route the lav to one track and the shotgun to the other. That gives you, or the editor if it's not you, choices in post. If you position the person so their body blocks as much of the other sound coming into the lav as possible that will help. If you are flying solo, then the lav is definitely your best bet unless you want to just lock off your camera shot and try to boom the audio yourself (but what if the talent moves out of your picture while you're doing audio?). Whatever you do, don't try to use just a camera-mounted mic.