How can I use control over the aperture to take better photos?

Question

I upgraded from a point-and-shoot to a Sony NEX a few months back. I think I've made substantial progress with regards to many aspects of photography like composition, the rule of thirds, ISO, exposure (shutter speed, exposure compensation, exposure bracketing followed by exposure fusion in Photomatix), low-light photography, using a tripod, using a timer to avoid camera shake, etc.

But I can't figure out how to control the aperture to take better photos. I just leave it to the camera all the time (Program mode), while controlling the other settings mentioned above.

Note that I don't shoot fast-moving objects (sports, people, kids, pets, wildlife, etc) so blur is not a problem. The other thing I can think of that control over the aperture gives me is depth of field control, but I can't think of ways to use that to my advantage. Can anyone give me some tips?

In case it matters, I have a f/1.8 35mm and a f/2.8 19mm primes.

Answer 1

Practice, practice, and then practice!

Force yourself to shoot in Aperture Priority mode and shoot the same subject from the same position using different apertures. Examine the results to see how different aperture settings affect the resulting images. This is best done from a tripod with a static subject so that the only variables are the change in aperture and the corresponding change in shutter speed computed by the camera to maintain a constant exposure value.

Answer 2

Taking control of aperture does not make for better photos. It makes for a more specific one. Even in Auto mode, the camera always shoots at some aperture which gives a certain result. Aperture priority mode lets you decide the depth-of-field and compromise between aperture and shutter-speed. The resulting photo is not absolutely better but will be of your choosing.

In order to make this work - which hard to go back once you get used to it - you need to first get to know depth-of-field and softness characteristics of your lenses. That means taking shots of different subjects at a variety of apertures and subject distances.

One you know what the result of shooting with a certain aperture is with each of your lenses, it will be your task to pre-visualize that effect on your next subjects. Then, you select the aperture before each shot, making it a conscious decision of how much to include in the depth-of-field and how to balance the resulting shutter-speed and ISO.

Sharpness will also be affected which is why it is important to know how your lenses behave. The widest is almost also softer and may not even be acceptably sharp depending on the particular lens. Small apertures will exceed the diffraction limit beyond around F/13 which you will also want to generally avoid.