It’s been observed that painting is an additive medium, whereas photography is a subtractive medium. In painting, you start with a blank canvas and add elements to it to build your composition (for example by painting a house, painting a tree next to the house, painting a blue sky above the tree and house, etc.), while in photography you start with a cluttered frame and subtract elements from it (for example, by moving the camera to exclude the fire hydrant in the foreground, zooming in to eliminate the gas station next to the house, etc.) until you have only the elements left necessary for the composition you are trying to achieve.
It seems to me also that painting is a medium concerned with the adding of realism, whereas photography is medium concerned with the adding of abstraction. In painting, you start with a blank canvas, the ultimate expression of abstraction. There’s nothing there, it can be anything you want until you start painting on it. The process of creating the painting is essentially the process of adding realism to it, right up until you reach the level of realism that you desire, be it a still-pretty-abstract piece of abstract expressionism, a somewhat-more-realistic work of impressionism, or a very-realistic work of (quite appropriately named) photorealism.
Photography is just the opposite. The nature of the camera is to produce an image that is perhaps the ultimate expression of two-dimensional realism. However, if you hold a camera up in front of something and simply click the shutter, the resulting image will be photo-realistic, but rarely will be pleasing. It takes the application of abstraction to make a photograph interesting, and the tools of the photographer are largely used to introduce abstraction into the photographic image. Such tools include, for example, camera placement, lens selection, long exposure, and dodging and burning, which were the tools used to in the making of the image in this post.