D.O.F or Depth of Field is the range of distance that appears sharp in an image, this is achieved with aperture and focal distance. Or in plain English its the area in an image that is super sharp where you focus your lens while the surrounding area seems to get softer or blurry. I love to use this in my images especially when I want to focus on just one subject while softening the background or other subjects to demand importance in a specific area of an image.
This is a great way to focus your attention to one area while the background is soft and pretty while being non-distracting. I use this a lot with sessions involving small children. I love images that focus on that small child while the parents are visible in the background but not the main focus. I often use picture frames to frame out the parents but the main focus is still the child. These often are some of the most popular images with the parents. In the session below I asked him to hold the frame and make a yucky face while I instructed the parents to have a quick smooch. 
Have an intimate moment for the parents in the background by having them kiss or simply a warm embrace while the child is brought forward for the main focus. Its an idea for the family unit to be present without taking away the focus of the kids. The little guy below was really engaged with me and my camera, and I simply asked the parents to hold each other close.
I have also used this technique for maternity sessions as well, here are examples of ways you can create unique images:
Use baby blocks to spell out the baby’s name or Include furry family member!
