There are a number of tricky issues that surround artists and copyright. One of the primary concerns is the use of reference photos, and it's a topic of much discussion among artists.
One question typically goes something like this: "If a photograph is in a reference book or field guide, can I legally use it to create a painting?" The answer is not an easy one, and it really depends on how you are using the photo. Is it purely for reference or are you copying it while you paint?
Using a Photo as a Reference
First of all, keep this in mind: books or websites are copyrighted, and the photos within them are also copyrighted, either by the publisher or the photographer. Just because a photograph appears in a publication that is intended to be a "reference" does not mean it's fair game for anyone to use.
In most cases, the photographer has expressly permitted for the photo to be reprinted in that specific publication. They are there only to provide information, most often to the readers who wish to identify things in nature and they should not be copied.
To truly use a photo as a reference, you would use it to learn about the characteristics of your subject. For instance, the shape of a particular tree, the texture of a rock, or the colors on a butterfly's wings. As an artist, you can certainly use that knowledge in your original compositions and paintings.
When It Becomes a Derivative
Quite often, the distinction most people don't make is the difference between using something for information (as a reference) and copying the image. When you are, for example, finding out how far the orange feathers of a bird species extends down the chest, that is a reference. If, however, you take that same photo and paint it onto canvas, that is copying it and making a derivative.
A derivative artwork is frowned upon, both ethically in the art community and the legal world. Some people argue that if you change 10 percent (the number varies), then it's yours, but the law doesn't see it that way. The 10 percent "rule" is one of the great myths in art today and if someone tells you this, don't believe them.
To put it plainly, a field guide is not produced so that artists can make derivatives from the photos. However, there are books and websites available that are filled with an artist's reference photos. These types of publications are produced with the intention that artists use them to paint from. They will state this very clearly.
It's About Respect for Other Artists
One question you might ask yourself is, "How would I feel if someone copied my work?" Even if they did change it, would you be okay with someone else doing to you what you're considering?
Beyond the legal issues, that is the reality, and what it comes down to, a photographer or another artist creates each photo, illustration, and artwork we see. It is unfair and disrespectful to them and their work to make derivatives of them.
If the painting is just for yourself, you can argue that no one will ever know. When you start to sell paintings or even share them online, in a portfolio, or anywhere else, it's an entirely different game.
If you're truly using someone else's photos or illustrations as a reference, you're collecting information and applying it to your painting. It's exactly like applying your knowledge of color mixing. When you use someone else's work in a full-scale painting, as the background of a collage, etc., that is not using it to gain knowledge.
Finding Photos You Can Use
There are many ways that you can find great images to legally use as a reference for your paintings.
First of all, it's best to err on the side of caution and ask before you copy a photo. Many photographers are happy to permit the use of their photos while others will want a fee. You can also find a source that allows for derivatives.
There are a number of websites that allow photos to be used in a variety of ways. One thing you'll want to look for is the Creative Commons license. Websites like Flickr and Wikimedia Commons allow users to share images with a variety of permissions under this type of fair-use license.
Another good source for photos is Morgue File. This website includes images that photographers have released, and they're actually meant to be adapted to new work. One of their previous taglines explains it all: "free image reference material for use in all creative pursuits."
The bottom line is that you need to pay attention to copyright as an artist and that does apply to reference photos. Think before you paint and all will be well.
Disclaimer: The information given here is based on U.S. copyright law and is given for guidance only. You're advised to consult a copyright lawyer on any and all copyright issues.