I thought of a lot of examples of depth of field where I tried to be funny and came up with the following... I couldn't think of a funny way to approach the subject. I guess I didn't inherit great creativity from my daughter... go figure.
Simply put, depth of field is that area in an image that is in focus - some say acceptable focus. The area in front of or behind the subject can either be in focus or out of focus, depending on the effect for which you are looking.
There are several factors that affect depth of field: apature, distance to the subject, iso, the lense you are using and shutter speed. What I will focus on here (pardon the pun) is apature because it has probably the greatest affect. Suppose you want to take a picture of your middle brat standing in front of a tree and you want the tree in a soft blur. This effect tends to draw attention to the middle brat (and everybody knows he needs more attention). You need to setup your camera with a large f-stop of f5.6 or larger (remember a larger apature would be f2-a subject for another blog). Then move in pretty close to the middle brat and shoot the picture. Focus on his eyes and everything behind him should be out of focus. That's it!
The sketch below will sort of give you an idea of depth of field in a quick glance:
Now for some examples. This first one was taken a f5.0 with a shutter speed of 1/15 and the iso set at 400.
The second example was shot at f16 with a shutter speed of 1/6 of a second. As you can see, it si completely sharp.
Have fun and practice...