Creative use of Depth of Field (DoF)

Control of depth-of-field is one of the most creative tools photographers and DSLRs have.  
But what exactly is depth-of-field?
In the most basic terms, it's the distance in front of and beyond the subject that appears to be in focus.


Choose your subject—that rose flower in your garden, for example—and focus on it. Depending on what you decide now, you can make the grass in front of that bush sharp or soft; likewise, the fence behind the bush.
Choose to let the foreground and background go soft and you've effectively isolated your subject and called specific attention to it. Choose to have the foreground and background sharp, and the rose bush becomes an element in the overall scene.
The key to using depth-of-field to isolate or blend your subject is lens aperture. Wide apertures, such as f/2.8 or f/3.5, provide shallow depth-of-field: your subject is sharp, but little else is.

Kishika, My Niece

A Tiny Flower

Narrow apertures, like f/16 or f/22, provide a much greater depth-of-field, so that the territory in front of and behind the subject will be in focus. I haven't shot anything like that yet but, I have shot enough landscapes where you want to get everything in focus.

Sunrise at Liberty International Airport, Newark, NJ

 War Memorial at Washington DC

Simply, the smaller the number, the shallower the depth-of-field; the greater the number, the greater the depth-of-field.


Selective Focus
I primarily shoot nature landscapes, skylines and depth-of-field, along with light, helps me create depth, texture and dimension in my pictures. I took Image 1 [Kishika above] with a my 18-55mm kit lens, and I shot wide open—meaning the lens aperture was at its maximum opening, f/4. Small number, shallow depth-of-field—which is exactly what I wanted. I really loved the glare in her eyes, and I wanted to accentuate the face details [nose and lips] as much as possible. 
By selecting the wide open aperture, I was choosing to have only a eyes, nose and lips in focus while everything else went soft [notice the ears and earings?]. This process is called selective focus, and the result in this picture is that the eyes really stand out—and your eye is directed to exactly what I want you to see.
Another example of how I use selective focus is Image 2 [Tiny Flower], which was taken with an same lens. As I photographed this flower, I thought the edges of the petals were stunning. I chose to make one of the flowers jump out of the frame by carefully composing the image, focusing on the flower and shooting at f/4—again, wide open. By using depth-of-field in this way, I created an image that has more impact than one taken at, say, f/5.6. The falloff is dramatic, and there's no doubt about my intended center of attention.
As you've probably realized, when you're shooting wide open, or at any wide aperture, focus is critical. If you're using a Nikon digital SLR, focusing sensors are located in several different areas of the viewfinder. When you're composing the image, make sure to select a focus point that corresponds to the location of your subject in the viewfinder.

When depth-of-field is going to be a critical part of your image, it's vital that you choose to shoot in aperture-priority mode—meaning that you choose the aperture and the camera automatically sets the shutter speed. Depth-of-field control means control over aperture.

Test Run
With a digital camera, you can easily and rather quickly get an understanding of the effects of depth-of-field simply because you can see the results almost instantaneously.
Try this: Pick a subject that has a distinct foreground and background. Focus carefully and using aperture-priority shoot a frame or two with a wide open aperture. Then continue to change the aperture setting until you're near the other end of the scale, say f/11 or f/16. Examine the images and notice how your aperture settings affected the images as the depth-of-field increased with every different setting (each time you close down the aperture one full stop, you actually double the depth-of-field).
With practice, you'll soon be able to anticipate what an image will look like at specific aperture settings. And experimenting with depth-of-field is also a great way to train your eye to see three dimensionally.

I will come up with a selective coloring tutorial next.