Tuesday, April 26, 2011
Filters On Filters • How Big Can I Go? • Focus On Flowers
Q I really like the treatment you give to field flowers, such as poppies and tulips, where you focus on one flower or a small group of flowers with the foreground and background blurred. How do you do that?
Via the Internet
A It’s a technique called selective focus, used to emphasize one plane of sharpness in a scene. The focal length and ƒ-stop of the lens are the factors that control the range of focus and the amount and look of the blurred features in the background and/or foreground.
A telephoto lens of 200mm or longer is the tool to start with because telephoto lenses have a narrow depth of field when photographing relatively close to a subject. A wide-angle lens positioned close to the subject will fill the frame, but also will capture any background distractions quite clearly. A telephoto lens positioned to fill the frame with the same subject will be farther away, but will throw anything in the background out of focus. The longer the telephoto, the narrower the depth of field the lens maintains when used in this manner. I’ve been known to use a 500mm ƒ/4 lens to photograph individual flowers from a considerable distance in order to apply this effect. Telephoto lenses can be made to focus at a closer distance by adding an extension tube between the lens and the camera. My favorite setup for these techniques is a 100-400mm zoom with a 25mm extension tube.
Adjusting the ƒ-stop (aperture) of the lens gives you some flexibility in interpretation of the subject and the background. A smaller ƒ-stop (ƒ/8) will expand the depth of field somewhat for a larger flower or a group of flowers, but it also will begin to capture detail in the background. I often set the telephoto lens at its largest opening (e.g., ƒ/4) to minimize the depth of field and expand the unsharp area, but at this aperture, you must be certain to accurately position the sharpness on the subject you want to emphasize.
A third factor that some photographers feel is important is the shape of the lens aperture; as you stop down, the lens opening is less round, so this alters the shape of highlights of the out-of-focus background. Personally, I don’t think this is a critical factor, but some invest in very expensive lenses that maintain a completely round aperture.
In considering the composition of selective-focus images, I frequently look for foreground elements, as well as background elements, that can be thrown out of focus. This gives the image more depth, and if the foreground is very close to the lens, puts a color wash in front of the subject that leads the viewer to it.
For information about upcoming seminars and digital-imaging workshops, visit www.georgelepp.com. If you have any tips or questions, address them to: OUTDOOR PHOTOGRAPHER, Dept. TT, George Lepp, 12121 Wilshire Blvd., Suite 1200, Los Angeles, CA 90025-1176 or online at www.georgelepp.com.
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