Here in Japan, many "manga-ka's", manga illustrators who's style is realistic, have assistants who can take reference photos for the artist. Artist can make a sketch or write a list and send assistants to the streets to find right kind of locations and take the necessary photos. Superb! I think I'll have to hire someone to assist me with photos! (I think they also have these kind of people working for Studio Ghibli?)

I do carry my digital camera with me all the time. I take photos of just about everything. Then I file them to my harddrive in folders, called for example, "Forest, trees", "Water", "Noise", "Sky, clouds" and so on. If I'm very busy then I just leave them laying on iPhoto and some day hope to find what's needed. But I have thousands of photos so I should take better care of them! Usually when I need something special, I can't find it and then I'll try to think how can I find this kind of location and then go there to take photos. Well... using assistants would be much easier!

Sometimes also bad photos can be used for a good purpose. So I usually don't erase any photos that look interesting even a little. Here's a example of a bad photo:
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And here's the book cover layout for Dave Egger's Finnish edition of "You Shall Know Our Velocity". (By the way, the white text is not really completely white, it's a semitransparent glossfolio on matt paper, it looks much cooler in real life.)810984.jpg