2. Setting Your Aperture/F-Stop
The basics on aperture settings are that: the lower the f-stop, the wider aperture, the shallower the depth of field. Alternatively, the higher the f-stop, the smaller the aperture, the deeper the depth of field. If you can remember this, you’ll be set!
That said, when shooting portraits, you’re better off setting a wide aperture (for example, f/2.8-f/5.6). Why? Because, portrait photographers want a shallow depth of field so that the background isn’t competing with the subject, making for a “busy” photo. A shallow depth of field makes the subject, such as an adult, pet, or child, stand out in the image. Their eye and hair color will stand out, and the background essentially serves as a curtain backdrop.
Shoot in Aperture Priority mode to control depth of field; in this mode your SLR will helpfully set the shutter speed for a correct exposure.
Specialist portrait lenses tend to have even wider maximum apertures (from f/1.4 to f/2.8) in order to blurbackgrounds further.
There may be some occasions when you want a deeper depth of field, especially if it’s a large group of people and you don’t want the people in the back row fuzzed out. This is another tip where some of it will be up to your discretion based on your immediate situation.
3. Exposure Compensation
Sometimes you might want to brighten your subject’s face slightly. Maybe you don’t have enough light directed on their face to take a great photo, or maybe your subject has darker skin. To do this, use Exposure Compensation.
Landscape photographers use this trick to darken or lighten skies, and you can use it for portraits. Here’s how it works: press the Exposure Compensation button (see your manual for your specific camera) and dial it up +1 stop of positive Exposure Compensation to lighten up people’s faces or -1 stop to darken it. I would start with 1/4 EV, and keep increasing or decreasing by 1/4 increments until the face looks just right.