TECHNIQUES: DEPTH OF FIELD

Our eyes can choose to have any particular object in perfect focus, whereas a lens has to choose a specific focal point and what photographers call a “depth of field,” or the range of distance to each side of the focusing plane which still appears to be in sharp focus.  This difference presents the photographer with an important interpretive choice: does one wish to portray the scene in a way that draws attention to one aspect by making only the aspect in focus (such as would occur during a fleeting glance), or does one instead wish to portray all elements in the scene as in focus (such as would occur by taking a sweeping look throughout).  Until recently, traditional night photography was especially restricted with this choice, because there is always a trade-off between the length of the exposure, the depth of field, and the noise levels (or film grain) for a given photo.  Where artistic flexibility is required, I often use a technique which utilises multiple exposures to create a single photo that is composed of several focal points; similar to how our eyes may glance both near and distant in a far-reaching scene.

If I were to stand in front of the above scene and take a quick glance, either the first or the second image would be closer to what I would see, depending on what I found interesting.  On the other hand, if I were to fully absorb the scene—analysing both the the stone carvings in the foreground as well as the bridge and trees in the background—then my view would be represented more realistically by portraying details for both regions, such as the final image on the right.  This technique allows me to decouple myself from the traditional trade-off between depth of field, noise or film grain, and length of exposure.  The end result is a print that is both less noisy and sharper in every region of the photo.

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