Understanding the concept of depth of field is essential to becoming a better photographer. If you're unfamiliar, depth of field refers to the areas of a photograph that are in focus. Images with a shallow depth of field have only a small range in focus while the background or the foreground is blurry. "By using a minimum depth of field, the petals on a flower will stand out. It can be a very strong effect, just like total depth of field can be," Steinmetz says. "But you want to use these things with meaning. It can't just be schtick."
For instance, a lens with a big f/1.4 aperture will create a shallow depth of field in a portrait, so your intended subject really pops. Landscape photographers, on the other hand, may want everything in their sweeping panoramas to look sharp and so instead will opt for an f/22 setting with a wide depth of field.