1. Aperture + Focal Length + Distance From Subject = Background Blur
A subtly blurred background can make a world of difference to portrait photography, and puts the focus squarely on your subject without having a swathe of background detail stealing away attention (as well as adding depth of composition when done right.)
The main method most people rely on to achieve this is to use a large aperture for a shallow depth of field (between f2.8 and f5.6 is ideal), but it’s not the only factor to consider.
For best results, use a larger aperture combined with a long focal length lens (around 55mm to 105mm should do it.) Another thing which will come into play is how far you’re standing away from the subject, which hinges upon the focal length you’re working with and the amount of space available, but balancing all three factors is the key here.
You could always isolate the background and apply a little gaussian blur in post production, but that’s time consuming and the results often turn out looking obviously manufactured. Save yourself a lot of headache by learning how to produce the effect right there in the camera.
2. You Can Move Things
Speaking of backgrounds and reducing visual noise, you’ll sometimes find yourself in an interior setting with a lot of junk in the background (if you’re photographing someone at work for their portfolio, for instance.)
This is one of the simplest tips in the book, but one which is often forgotten: you’re allowed to pick something up and put it out of shot.
Whether it’s through trying to be polite in someone else’s environment or through fear of being too obtrusive, many photographers – even professionals – seem to get shy about clearing the shot of junk.
Don’t be. During brief period of time that you’re shooting, that place is your studio and you owe it to whoever you’re photographing to roll your sleeves up and set up a killer shot.