Need for Speed
by Bjørn Rørslett 

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Why is it some lenses can throw the background so completely out of focus? A very large aperture is part of the answer. Another is the ability to focus close. If you want something extraordinary in your pictures, read on to learn more. Even lenses obtained for a low price on a fleamarket or garage sale can be pressed into useful pictorial service.

Back to the Future

Wild, Soft & Sweet Berries

© Bjørn Rørslett/NN

Nikon D1X with Rodenstock TV-Heligon 50 mm f/0.75 lens

I often want a distinctive look and feel to my pictures. The field of close-up photography, always being a favourite occupation of mine, offers attractive motifs and inherent shallow depth of field as well. Traditionally, many people including myself employ specialised lenses ("macro" lenses, Micro-Nikkors) to record the close-up images. These lenses do provide valuable features such as image field flatness, excellent sharpness, and low amount of chromatic aberration. All of this is desirable for shooting flowers, coins, stamps or other small objects which need to be depicted as perfect as possible, but at the same time, such perfection may dull the resulting visual presentation. So, at least as an alternative, other visual approaches might be explored, and while doing so technical trade-offs should be accepted. My preferred choice is shooting with fast lenses at wide aperture settings. In fact, the wider the better and don't let the f/1 barrier hold you back.

Very fast lenses provide you with benefits in several areas. Firstly, a large aperture means you see a brighter and clearer image in the viewfinder, thus making it easier to compose and focus the picture. Secondly, you get a faster shutter speed throw into the exposure for good measure, thus enabling easy-going, relaxed and hand-held shots for many situations in which tripods normally are needed. And thirdly, you get that elusive soft yet sharp image rendition only attainable with extreme apertures. Outside the plane of sharpest focus, everything is not only blurred, but washed out of existence. Thus you get a layer of abstraction added to any image shot with such high-speed lenses.

You might wonder whether this softness could easier be achieved by slapping on a soft-filter on a more modest lens, or - heavens forbid - created in Photoshop? I really don't think this to be a feasible option, although opinions clearly may differ here. Soft filters certainly can soften the image, but do not influence depth of field. Photoshop wizardry of course can play clever tricks with sharpness distribution of a digital image, but you need to massage the image file a lot to create even a remote resemblance to what a large-aperture lens can produce in a split second.

Need for Speed

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Last Update 24 December, 2002