Photo tips for watery bloggers -- Depth of field

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Infinite focus -- 7.2mm @ f/5.0

The apparent depth of field within an image is a result of aperture and focal length.

Infinite depth of field can be created by closing the aperture of any lens down to f/5.6 or smaller, and adjusting the calculated focus range to be what the photographer wants the image to reflect. On all manual lenses and some of the newer auto-focus lenses this is easily achieved via the etched markings on the lens barrel -- a process called zone focusing or scale focusing. Naturally the zone of focus expands with the smaller apertures but this comes with degradation of the image, as lenses always deliver their best results in the mid-range of their apertures.

Infinite focus -- 24mm @ f/5.6

Infinite focus -- 7.2mm @ f/4.0

Telephoto lenses are well known for creating shallow depth of field with near focus subjects, they can deliver results that illustrate a very sharp transition from focused subject to out-of-focus background -- depending on the lens aperture, specific focal length and image chip size.

Close focus -- 210mm @ f/6.3

With the recent explosion of digital photography and sharing of images on the Internet, less familiar photographers are coming to realize that shorter focal length lenses are also capable of shallow depth of field shots, with even better results because the transitions from sharp focus can be very creamy and soft, adding a sense of dimension almost impossible to achieve with telephoto lenses.

Close focus -- 50mm @ f/0.92

Portraits can be greatly improved by using a shallow depth of field, since the technique helps to soften and hide skin imperfections without any assistance from Photoshop. Additionally, if the inside of the closest eye is used as the lens focus point, that instantly becomes the focus point of the entire photograph in its finished state.

Close focus -- 85mm @ f/1.2

The take away here is that selective depth of field control is hard to achieve without the means to do so, and it's a function that's becoming more and more difficult to find on inexpensive cameras.