As Larry said, photos for a particular camera (with particular settings) are similar. If you take a lot of movies, those are generally a lot large than still shots. Longer movies are generally larger than short ones. Higher-definition/resolution movies and photos (as determined by the camera/phone) are generally larger than low-definition/resolution ones.
Have you already determined that your Photos library is the problem? For a quick check, do a Get Info (command-I) on the library in the finder. For a more detailed analysis of your storage space usage, you may want to look at a specialized program like OmniDiskSweeper or GrandPerspective.