Depth of Field

Depth of Field

Lens Depth of Field

To begin with, depth of field (DOF), what it is and how to understand how to use it.

DOF can be viewed as the amount of a picture that is in focus. As a matter of fact, this could be a short/narrow DOF to a long and wide DOF. Generally speaking, three factors determine the DOF.

The focal length of the lens

In the first place, the focal length of the lens is the ability of a lens to magnify the image of a distant subject. As a result, it is the distance in mm from the optical centre of a lens to a point where a subject at infinity appears in sharp focus. This is usually the cameras digital sensor. In this case, think of this as the physical length of a lens in very simple terms.

Picture of Focal Length Headshots

Aperture

In the first place, each lens has a maximum aperture and a minimum aperture. As an illustration, the range could be from f2.8 to f22. In other words, this means the amount of light that can enter through the lens. At the same time, the small f-number (f2.8) allows loads of light to enter the aperture which is wide open. On the contrary, the large f-number (f22) allows the smallest amount of light in. As a result, this means the aperture hole is small.

Sample of aperature openings headshots

Distance

Different distances decide what the DOF is likely to be. If you are photographing something at distance you are going to get an image where most things are in focus. This may mean that anything close to the camera is out of focus. On the other hand, if you photograph something close then the subject close to the camera will be in focus. You will also notice that the background is blurred or out of focus.

What DOF can do for you?

A shallow depth of field is great if you want to make your subject stand out. That’s a portrait subject with a nice out of focus background. This means the subject stands out no distracting background.

For a landscape photograph, the camera’s lens can only focus on a single point. This means that areas before and after this point will appear out of focus. Although in reality, the area in focus will be a lot of the image. The out of focus will be near and far away from the lens.

Picture of a candle holder at f2.8 Depth of Field
Candle Holder at f2.8
Picture of a candle holder at f8 Depth of Field
Candle holder at f8
Picture of a candle holser at f22 Depth of Field
Candle holder at f22
Picture of a candle holder at f32 Depth of Field
Candle holder at f32

DOF Apps

The Depth of Field is notoriously difficult to work out when you first start to understand it. The good thing is that apps for mobile phones are available that take the guesswork out of it. For apple phones here is a link.

To find out more contact Martin

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