Behind the Lens: depth of field for portraits

Jim McKenna in Lake Placid. Photo by Mike Lynch

Photographers regularly use depth of field to their advantage when taking portraits. They do this by creating a shallow depth of field, which results in subject being in focus and the background being blurred out.

This method allows your subject to stand out, especially when there is a distracting background.

Photographers will use longer lens and large apertures – achieved by setting the f-stop to a smaller number – to get this effect. Choice of background is also important, though sometimes you don’t have good options.

In the above photo of Jim McKenna, I was able to find a pleasing background, so I didn’t need to think much about obscuring the background. The background was also pretty clean, which is what you aim for with many portraits.

In taking this shot, I set the aperture to F/4 and picked a focal length of 70 millimeters. This allowed McKenna and the fence to stand out, as they were in focus. Meanwhile the mountains behind him were just slightly blurry.

If you don’t have a good background to work with when taking a portrait, that’s when you often have to rely on using a larger aperture. If you use the manual setting and set your aperture to a smaller number such as f/2.8, it will create a large opening in your lens, and result in the background being blurry. In contrast, landscape photographers will set the aperture to a higher number, such as f/16, and create an image with more of the subject matter in focus.

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In the photograph below of forest ranger Julie Harjung, I used a lens with a length of 135 and set the aperture to f/2. These settings caused the distracting background to be mostly blurred out. The background isn’t necessarily my favorite, but I felt it was blurred enough for the purpose of this news photo.

If you don’t own a DSLR or mirrorless camera with manual settings and interchangeable lenses, many smart phones have a setting that allows you to create the blurred out effect. My smart phone has a portrait setting, which I would have used for the image of Harjung. However, I would have considered leaving the smart phone camera in its normal mode for taking the shot of Jim McKenna because of the pleasing background. In the case of McKenna, I’d probably take one image in each mode in that case and see which one I liked better. It’s always good to have options.

Forest ranger Julie Harjung. Photo by Mike Lynch

Behind the Lens is a regular column by multimedia reporter Mike Lynch about photography and his assignments. It appears the second and fourth Wednesdays of the month.

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