I'm putting together a handbook for students going abroad on travel photography, and these are a few I collected for it:
The camera cannot lie, but it can be an accessory to untruth. ~Harold Evans, "Pictures on a Page"
The quote in my signature!
All photographs are accurate. None of them is the truth.
~Richard Avedon
If you take a picture of a human that does not make him noble, there is no reason to take this picture. That is my way of seeing things.
-Sebastiao Salgado
And this longer passage by Allard I really like:
If a subject has a delicate surface to it, you do not want to go charging in there. You need to establish some kind of presence and understanding. I will say, 'Try to forget I'm here. I won't ask you to pose, I won't ask you to do anything.' It's important that I just be allowed to be around, to be present. Photographing people requires a willingness to be rejected. So, I think the best approach is to be honest and direct. Very often, I tell them, "You don't know me. There's no reason why you should trust me...the only thing I can promise is that I'll try to do the most honest work I can. Ultimately, it comes down to somehow being able to instill confidence. I don't think you can bull**** your way into that, because a lot of these people can see through walls. If you want to photograph people, you'd better know something about them. I like to explore, to be sensitive to the rhythms of the moment. Exploration means seeking out what I think is there, and yet often finding something finer, something closer to the center, that no amount of research could have led me to. I tend to react more than direct. You have to be receptive. You have to care. You can't do good work if you don't care. That's not necessarily a strength, but it gives you strength. –
~William Albert Allard, "Photographic Essay (American Photographer Master Series)"