Photos from these collections need to be purchased. They are rights-managed, and some may be royalty-free. Conditions for use vary among the databases, and should be checked.
Images are available from a variety of online sources. Websites containing images may be freely accessed, or may be accessed by subscription or password only, but that does not mean that the images can be freely used in print or online publications. They may be freely accessed, i.e. looked at, but in all cases, there are standard rules that cover the use of images.
Creative Commons (CC) is a not for profit organization that helps the public to share creative content by providing free licences and tools to content creators. CC content (including images, music and artwork) may be shared and reused according to the CC licence applied.
Quick tips on using images with Creative Commons licences:
Photos from these collections can be downloaded free, but may be rights-managed instead of being royalty-free. The attribution requirements may vary, and are indicated in each database.