In photography, depth of field is the portion of a photo that appears sharp. Lenses can only focus on one object at a time, but you can control what is in focus in your photograph by using your aperture (see lesson on aperture if you don’t know what I am talking about).
When photographing a landscape you would usually want a lot of the picture in focus. You would use f/16 or f/22 for a landscape. If you use f/22 you are going to have a lot of the photo that will be sharp. In photo terms, you will have a deep DOF.
If you are photographing a person (portrait) you are usually going to want a shallow DOF so the background will be out of focus. Most portraits are taken at F/8. The reason for using F/8 is that at this fstop (aperture) an average person’s head will be in focus and the background will not be in focus. Not having the background in focus will draw attention to the subject. Now if your subject has a huge head (we used to call my little brother pumpkin head cause his noggin was big; we don’t call him that anymore cause he is about 6 inches taller than me and he would kick my @#%$), use a smaller f/stop like f/11 or f/16. Really, I’m just kidding, f/8 should be a standard for most portraits.
There are three things that determine DOF.
1.Subject distance (how far away the subject is from the camera). The closer a subject is to the camera the shallower the DOF is.
2.The lens focal length. If you are using a 500 mm lens there will be less DOF.
3.The lens f/stop(aperture). You should know what this is from the lesson on f/stops. Basically, the wider your f/stop is, f/4 or f/5.6, the shallower the DOF will be. That is why if you are shooting a landscape you want to use f/22 or f/16, because you will have a lot of DOF.
Shallow depth of field -taken at f2/8
Medium DOF. Taken at f/8
Deep Depth of Field f/22
You can see the diffences in how much of the photograph is in focus. With the headshot of the little girl, only her eye and a few strands of hair are in focus. The middle photo of the hitchhiker was taken at f/8. This makes the subject in focus and while the background is out of focus. In the lake above the whole thing is in focus. This photo was taken at f/22. Imagine if I had really shallow DOF on the lake. The trees in back would be out of focus or maybe the front of the photo would not be in focus. That would not make for an interesting picture.
I hope I have been clear. If you need help or do not understand, post a comment and I can help you more. Anyway, thanks for visiting my blog. Bookmark me and visit often, and if you need anything -specific lessons or tips- let me know.
Oh, and if my pumpkin head brother reads this I want him to know that I hold him in the highest regards. You are a wonderful person, Chris.
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