Understanding and manipulating depth of field in an image is a key skill of professional photographers.
A firm grasp on this concept can improve the quality of your work and can provide you with countless alternative ways to shoot one subject.
Although it may seem confusing, with a little practice it will quickly become second nature.
What is it? One way to think of depth of field is how "deep" the focus goes in a picture.
Put more simply, it refers to how quickly items in the background lose clarity compared to the focal point of the photograph.
It can also be thought of as the relationship between blurry elements and focused subjects in your picture.
For instance, a photograph of a flower with the entire background showing as blurry would have a low depth of field, while a photograph of a long subway platform with both near and far subjects in relatively clear focus would have a high depth of field.
In either of those examples, changing the depth of field would have a dramatic impact on what the viewer experiences when looking at the final image.
How Do You Control It? The primary influence on the depth of field of any particular image is the length of its exposure.
The longer a digital sensor or film has to absorb the image it's being exposed to, the more detail it will accurately capture in the image.
Any time you have longer exposure times, you'll always have a greater depth of field in your image.
In terms of manipulation, you can control the depth of field of any image directly by forcing the exposure time to either speed up or slow down.
You can do this by changing the shutter speed of your camera; slow speeds (60 and lower) will cause longer exposures and greater depth, while fast speeds (125 and higher) will decrease exposure times and cause the opposite.
Although you can intentionally make your images have greater depth of field, this will require you to adjust the aperture settings of your camera manually.
Since a longer shutter speed is needed for greater depth of field, less light is allowed to enter into the lens.
If you up your exposure but you don't close the aperture on your camera your photographs will be end up over-exposed.
Adjusting the aperture requires only moving the f-stop (usually a ring around the lens behind the focus ring) to whichever value will allow for the ideal amount of light.
Any new camera will let you pick a shutter speed and then will automatically adjust the f stop, but with older cameras, you'll have to play around with the light meter until the shutter speed syncs with the right aperture setting.
Helpful Tip: If you're working with high depth of field images it's likely that you'll be working with very long exposure times (depending upon the quality of your light).
Taking pictures like this will usually require a tripod to prevent camera shake and image blur.
Depth of field is an important concept to understand and properly apply to every picture you take as it's a critical component to every photographer's arsenal.
All subjects or objects in a picture have a story to tell so how you decide what's in and out of focus will impact the outcome of that story.
Consider how you could use it to impact what you can say about your subjects as this will help make your images more powerful and interesting.