Depth of Field is something which is misunderstood because of various technical terms like "circles of confusion," "hyperfocal distance" and other technical stuff.
So this time I thought about giving you an easy understanding about depth of field.
Auto focusing is not a new invention. It has been around for thousands of years as a feature of the human eye.
If you look at something in the foreground, it appears sharp. If you shift your eye to look at the background, this snaps into focus.
Much the same happens when you take a picture with your camera. The lens can only focus on one distance. Anything closer to or further from the camera will be unsharp. The difference is that the view is captured as a two-dimensional image. When you look at the image, only subjects at the focused distance will be sharp.
The area of apparent sharpness in an image is called the 'depth-of-field', and it is one of the main creative controls you have.
Depth-of-field factors
There are five main factors that affect depth-of-field.
Aperture
The lens aperture is the easiest way to control depth-of-field. At small aperture the area in focus is more as compared when the aperture is big.
Focal length
You will usually choose the focal length to suit the subject rather than to suit the depth-of-field.
At wide-angle lens magnifies the subject less than a telephoto lens, which means that more of the image appears sharper.
Subject distance
The greater the distance between the lens and the subject, the greater the depth-of-field is.
In Close-up photography the opposite also applies – increased magnification gives a narrower depth-of-field.
Print size
Depth-of-field appears greater in small prints than in big enlargements from the same negative or digital file.
Viewing distance
However, print size is less important than it might appear, because you normally view big enlargements from a greater distance than you view small prints.
As the viewing distance increases, so does the apparent depth-of-field.
Setting depth-of-field
As you can see, defining depth-of-field is a fairly arbitrary affair. So how can you hope to control the results produced by your camera? Here are few options.
Basic modes
Using one of the Basic modes settings available on some EOS cameras would save you time and trouble.
Aperture Priority Mode
This mode lets you choose the Aperture (the size of the hole in your lens) and let the camera choose all the other settings
If you want a wide depth-of-field, set a small lens aperture
If you want a narrow depth-of-field, set a wide aperture
Auto Depth Mode
It's called A-DEP mode. The term is shorthand for Automatic Depth of Field, or just Automatic depth.
All you have to do is compose the image and as you press the shutter button, rest will be done by the camera.
Not all cameras may have this option.
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