Portrait Photos

In previous posts, I've explained the impact of aperture upon depth-of-field.  When taking portrait photos, a commonly desired featured is a blurred background, as shown in the following photo:

My daughter, Tess, before her senior prom.
1/125 sec, f5.7, ISO 125, focal length 155mm

There are still more features in the background than I prefer, but they are fairly blurred so that the focus is literally upon her.   Better yet is the following image in which the background is completely blurred:

My daughter, Tess, before a previous prom.
1/1600 sec, f5.7, ISO 1250, focal length 300mm

Notice that in both cases, the aperture was f5.7, not extreme.  Instead, the shallow depth-of-field and resulting blurring of the background was due to using a longer focal length, 155mm in the first and 300mm in the second.  In both cases, I was using a Canon T6 with a zoom lens.

This narrowing of the depth-of-field is a strong reason for using a longer lens for portrait images.  A second reason is that the photographer need not be very close to the model.  I was probably 20 feet or more from my daughter in both cases and could take multiple candid shots without her being painfully aware of my presence.  Depending on the comfort of your model with being photographed, this may be a tremendous advantage.

The weakness of using a long lens is the general need for better light or a more expensive lens.  Many photographers who specialize in portraits will spend the money on a fixed-link lens (prime lens) of 80 or 90 mm.

Another reason for using a long lens is simply to take photos at a distance, such as when my older daughter was on the field at a track meet:

Ananda (left) and her friend, Kat.
1/500 sec, f8, ISO 400, focal length 300mm

Notice the lack of detail in the grass behind them.  That said, if you depend on the camera to do the focusing, the shallow depth-of-field may result in something other than your intended subject being in focus.  We'll leave focus issues for another post.