I was recently contacted by a friend with a common problem. She needed to get some good photos of her son, who was all dressed up for a senior high school ball. She has a good Nikon SLR and a good eye, but needed some tips on how to get the best from the camera.
It's approaching winter here, so the shots would be inside, so my first point was: don't use the built-in flash. The flash on cameras should be used as a last resort (your child being born as there's a power failure or aliens landing at night come to mind). If you have a flash unit (one you slip into the hot shoe on the top of the camera), it could be used with a suitable reflector or by being bounced off a white wall or ceiling, but the built-in flash is too small, and more importantly, too close to the axis of the lens. Built-in flash results in red eye and that "deer in the headlights" look. Don't use it.
The good news is that modern digital cameras can produce good results at quite low light levels. Perhaps as important, they can cope with the mixed light temperatures (meaning the colour of the light) coming from the variety of light sources we see in most houses. So, set your ISO on "auto", turn on all the lights in the room, and you'll probably get away with it.
Next, keep away from walls. Standing too close will probably mean your subject will cast a shadow and you'll end out with that weird "outline" around your subject. (That goes double if you use flash.) Get them to take a generous step away and all will be well.
Next, chose a good lens focal length. If you're using a full frame camera (e.g.: Canon 6D or the Nikon D750), then you will want a lens in the focal range 50 to 80mm (or thereabouts). Any shorter, and people will have those big noses and door frames will be curved. Longer than around 80mm and you probably just won't have the space needed - inside at least. If you don't have a full frame, you'll have an "crop frame" camera, which means your sensor is smaller than full frame and this will change your effective focal length. In practice, this means:
|Sensor Size||Indicated focal length||Effective focal length|
Preferred portrait focal length.
Great choice for portraits
A great portrait focal length
By the way: a "prime" lens (that is, a lens which doesn't focus) will almost always be better than a zoom, and particularly on the APS-C cameras, the "nifty fifty" 50mm lenses are ridiculously good for their price. As you can see, a 50mm on a crop frame is really a 75mm, which makes it a great portrait lens. If you're interested in portraiture, the nifty fifty is definitely worth consideration.
Getting exposure correct
The next point is about exposure. I've already mentioned keeping ISO on auto. Switch your camera to aperture priority and then select a big aperture, like f/4 Les and you will have a nice shallow depth of field or focus. Your foreground and background will be nice and blurry, and if you've focussed on your subject's face, they will be nice and sharp. In this image, I didn't want any detail in the background, so I chose a big aperture.
If you want the background in focus, go the other way and choose f/8 or f/11. Your camera will do the maths and work out the optimum shutter speed and ISO. In this environmental portrait, I wanted to emphasise Claude's deep interest in wood working and wood working tools, so I kept the depth of field as deep as a I could.
If all that's a bit much, use Program mode - but please don't select the green setting. Under that setting, you're turning your expensive camera into a basic point and shoot, and among other things, the camera will probably trigger flash.
Posing your subject
I guess that just leaves how to pose your subject. That depends on the style of the portrait, the personality of the subject and the circumstances, but you can get some hints on the web. You might like to check out these suggestions from the Digital Photography School for women and these for men. There's quite a difference between posing men and women - best poses are diametrically opposed for the most part.
So that's it. Not rocket science, and as you become more familiar with photography and your camera, you will come up with your own ways of doing informal portraits. But this is a good start.