Derivative WorksCollage is considered a derivative work. This means that collage incorporates elements of other works. (Other examples of derivative work include: a screenplay based on a novel, a biography that includes letters and journal entries, a piece of music that "samples" other recorded music.)
For a derivative work to be copyrightable, it must be "different enough" from the original works that it can be considered a new work in its own right. For most collage artists, this is not a problem. The very nature of collage generally involves combining multiple elements to create a new whole. However, keep in mind that the changes must be significant. Minor alterations to a single other work might not be "different enough."
Most important to the collage artist is that a derivative work can only include copyrighted material if it is created by the owner of the copyright on the original material, or with that person's permission. This means that making a collage that includes photos from National Geographic, Rand McNally maps, or pictures of Andy Warhol paintings, is illegal unless you have obtained permission from whoever owns the copyright on those works.
I have been told that copyright law does not apply to collage as it does to other derivative works, because collage is recognized as a special art form worthy of special protection. Nothing in my research confirms this or anything like it. So I am sadly forced to classify this as a myth. (Would that it were true!)
Please note that the law is unequivocal: "Only the owner of copyright in a work has the right to prepare, or to authorize someone else to create, a new version of that work." This means that, if you want to get technical about it (and I assume you do, or you wouldn't be reading this) an unauthorized derivative work is illegal from the moment you create it. It doesn't matter whether you publish 5 copies or 5,000. It doesn't matter whether you sell the collage for profit or give it away. The act of creation is the infringement.
There is a doctrine called "de minimis", which states that copyrighted material can be used in a derivative work without permission, if only a minimal amount of the original work is used. This sounds like it should be the answer for collage artists.
Unfortunately, the law is rather vague on this point. There's no clear definition of how much is too much, either in terms of a percentage, or total words or square inches. Even a tiny amount of copied material can exceed "de minimis" if it comprises the essential part of either the original work, or the derivative work.
Myths on creating derivate works abound: it's not illegal if you don't publish it through a large publisher, it's not illegal if you don't keep the profits, it's not illegal if you sell the original work but don't reproduce it. The reality is that creating a collage which infringes on copyright is illegal. No matter what you do with it.
Realistically speaking, if you create a collage and hang it on your wall, the copyright police are not going to come banging on your door. If you make a few dozen copies and give them to your friends, probably nothing will ever happen. If the original work is so altered that no one, not even its creator, can recognize it, then you are in the clear. But now we have left the question of "what is legal" and moved to the question of "what can you get away with." That's for individual artists to decide for themselves. However I have added a page to this site, "Theory and Reality," that discusses the issue in a little more detail.
So. We cannot create collages without the permission of original copyright holders (which is generally difficult to impossible to get). How, then, does collage ever get made?
The safest approach is to use only material which is not under copyright, or is copyrighted by you. Rather than clipping photos out of magazines, take photos yourself. You can often do a lot by using actual objects in your collage, rather than copyrighted photos. If you need painterly textures, make them yourself rather than using a photo of someone else's painting.
This may seem like an undue burden on the collage artist. But look at it from the other perspective. How would you feel if you opened a magazine and discovered someone else had used your work as part of their own, without asking or even informing you? Some say they would be flattered. It has happened to me and let me tell you, I was not flattered. I think when the shoe is on the other foot, then artists understand why copyright infringement is called theft.