How to use depth of field

"Depth of field" is a terminology that photographers use to refer to the range of the nearest and farthest subjects in a photograph composition that appear to be in sharp focus. Our eyes are able to choose to see subjects in sharp focus but camera lenses need to have a specific point to do that. This point is known as focal point or depth of field.

The difference in terms of depth of field created by varying objects distances can be especially useful to capture a portrait style photo. However, there must be a certain distance between the subjects and background in order for this technique to work. Subjects that are very closed together in terms of distances may not work well in the result of photo taken.

You probably have seen photos where the background is blurred but the main subject is in sharp focus. This is easily done with a DSLR camera but not necessarily easy for a point and shoot camera. The image below is taken by manipulating depth of field.

Notice that the background is blurred in the portrait style photo on the left. In this photo, there is a great distance between the boy and the background. If the boy is leaning on a wall for instance, the wall cannot be easily blurred out because the distance between the boy and the wall would be too close to reduce the depth of field. Recall on the previous post regarding the rule of third. This boy is not centered in the image. It gives more space. I would prefer that the image is zoomed out a little for a better result.


The photos on the right shows what can be done with field of depth if you have many subjects with many varying distances between them. Notice that the second girl (from right) is in sharp focus while the others are blurred. This technique is best done with manual focus, not auto focus on your DSLR camera. To try out this technique, you can set your camera dial to "A" for aperture priority mode. I prefer this mode because I don't have to worry about the shutter speed and at the same time concentrate more with the amount of light to be used. This can be done by adjusting the desired aperture opening, designated by F-stops. Do note that the smaller number of F-stop indicates a higher aperture setting. It means more light will be captured and reflected in your image.

Here's how you can do it:

1. Set dial to "A" for aperture priority mode. Some cameras use different abbreviation to denote this so you have to check with your camera's manual.
2. Set focusing to Auto Focus if you have a single subject with a resonably far background. Set it to Manual Focus if you have more than one object instead.
3. Set your aperture. In a low light condition, set a smaller F-stop number such as F5 for instance. On a bright sunny day outside the building you can opt for a higher F-stop number such as F22. Experiment with the F-stop number. You don't have to worry much since the shutter speed is determined automatically for the F-stop number that you set. But make sure your shutter speed is not too low to avoid camera shake and result in a blur image. As you set your aperture, observe the shutter speed. A shutter speed of 1/60 and above should do the trick.
   
4. In Auto Focus mode, you might need to use the steps described in the previous post (rule of third). Simply place the subject in the middle and press the shutter release button half way to activate auto focus. Without releasing the shutter, recompose your subject and press the shutter release button fully to shoot the photo.
5. In Manual Focus mode, simply compose your subject and focus manually onto the subject which you want to be in sharp focus. Turn the focusing ring on your lense to get a sharp focus of your desired subject. When the subject that you want is in sharp focus, press the shutter release button all the way down.