Depth of Field in Photography

A couple of weeks ago we studied depth of field in my digital photography class. Depth of field is what makes things look in focus.I learned that two things affect depth of field: aperture and lens length. A smaller aperture gives you a larger depth of field. A shorter lens also gives a larger depth of field.

Large depth of field is good for shots where you want everything to be in focus. (Another trick is using hyperfocusing.) To get the largest depth of field possible with my equipment, the top photo was taken with my wide-angle lens at 17 mm, its minimum focal length, with an aperture of F22, its smallest setting. The branches in the foreground and the buildings and trees in the background are in focus.

The photo at the bottom was taken with my 50-200 zoom at a focal length of 100 mm and an aperture of F 5.6, its largest available setting at that focal length. Same shot as above, just different aperture and lens focal length. Its shallow depth of field emphasizes the arbor vitae branch that I focused on while everything else in the photo is out of focus. Shallow depth of field is particularly good for portrait shots.