Differential or selective, focus is an extremely powerful in-camera technique that will help add finesse and style to your images. The effect is largely achieved with a combination of close focus, wide aperture and long lens (see below). Although a similar result can be created in Photoshop or similar photo editing software, it is long-winded and a lot more difficult to produce a natural looking image. It is much better to get it right in the camera in the first place. Another factor that can help to create a differential focus is digital sensor size. Depth of field becomes greater the smaller the sensor therefore it is much harder to throw your subject off focus with smaller sensors.
Full frame sensors such as that found in the Canon 5D Mk3 and the Nikon D800 have a great advantage here. This is the reason why some professional photographers like to shoot their portraits using medium format digital backs, as this gives them much greater control over what is and isn’t in focus… a very useful and creative tool indeed. DX size sensors or cropped sensors have considerably more depth of field at any given aperture, so it becomes much harder to use the selective focusing technique. Therefore if you want your subject to be un -sharp, you must try to use a combination of these factors and a little bit of Photoshop magic.
Lens choice for selective focus technique
The choice of lens for shallow depth of field in order to give effective selective focus is of the longer focal length variety. For example prime lenses such as a 135mm, 200mm and 85mm will give excellent results. Also, zoom lenses, such as 70-200mm are ideal for this purpose. Wide angle optics, on the other hand, (21mm, 24mm 35mm and wider) give a much greater depth of field for any given aperture and are therefore not as suitable for isolating a subject with selective focusing.
Another factor to consider is the choice of aperture. The larger the aperture, the shallower the depth of focus. It therefore stands to reason that wide aperture lenses such as F2.8 are very good indeed, when used at wider aperture settings, for creating a shallow focus plane which will make the subject stand out in the picture. My personal favorite lenses that I like to use for my portrait photography are the Canon 70-200 mm f2.8L IS lens and 85mm f1.2L Mk2 prime lens.
By Philip Lord from PJL Photography. Phil specializes in Portrait Photography Blackburn and over the UK. Keep up to date with Phil’s advice on Facebook.http://www.pjlphotography.nethttp://www.facebook.com/philiplordphotography
Article Source: EzineArticles.com
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