When someone asks me what the main difference is between shooting portraits and shooting real estate, the first thing that comes to mind is depth of field. Photos of brides and infants tend to have large areas of the frame that are artistically out of focus. In my opinion, everything should be in focus in a good real estate photo. To keep everything in focus, you will need to pay particular attention to your aperture and your focus distance.
Your aperture, or F-stop setting, controls how wide open the lens is. A low F-stop such as F/2.8 (large aperture) is wide open, gathers light very quickly, and provides crisp focus on a small depth of field. Much of the composition will be out of focus in low aperture, and the shutter will be relatively fast. F/2.8 may be great for portraits but it won’t provide the best results for shooting real estate.
To ensure that an entire room is in focus, I always use F/8 or higher. With large F-stop selected (small aperture) the lens opening is relatively small, gathers light slowly, and therefore takes much longer to form a composition. Any of you still trying to shoot in “Auto” mode will need to switch to either Manual or Aperture mode to achieve desired, high aperture settings indoors. Typically when we are indoors, it is a low-light situation. Auto mode on most SLR cameras will insist on F/5.6 or lower in low light, unless you override it. As you force the aperture smaller (large F-stop), it is crucial that you use a tripod, since your shutter will often be slower than 1/40 of a second. Most people can’t hold a camera still at these settings, especially after numerous caffeinated beverages.
If you are good at it, use manual focus. And don’t forget to keep an eye on your focal distance on every shot. As the size of the room you are shooting changes, you will need to adjust your focal distance. Moving from exterior to interior will require a vastly different focal distance as well.
For most of us using auto focus, you simply need to pay close attention to where the camera is focusing. Make sure that the camera is not focusing on unimportant things in your foreground (e.g. bushes, counter-tops, furniture) as this will increase the likelihood of important stuff further back in the scene being out of focus, even at high aperture settings. If necessary, force the camera to focus on something at the correct depth by pointing it directly at the subject, and then return the camera to desired location and finish the shot.
When it is apparent that something in the foreground (or far away background) could distract the auto-focus function of your camera, I always take multiple photos. Use your ears to determine if the auto-focus is working to find a focal point between shots and take 3 or 4. One of them is bound to turn out right.