AboutDave Nyce Expertise I have used SLR cameras for 30 years and have taught classes on photography at work for my co-workers. I had a darkroom for 20 years, but now am using mostly digital cameras. I can answer questions on equipment and techniques for photography, but am not an expert on specific model numbers of cameras or accessories.
Expert: Dave Nyce Date: 9/2/2007 Subject: blurred background
Question Hi Dave, I have just upgraded from an all-auto focus camera to one with manual options. How do I get the effect I've seen in some photos where the subject is focused, and the background is "blurred?"
thanks, Deb
Answer There is a property called "depth-of-field". It is the distance over which objects remain in focus. When the aperture is narrow, the depth of field is long. When the aperture is wide, the depth of field is short. A larger f number selects a more narrow aperture. e.g. f 22 means a narrow aperture and a long depth of field, so with f 22, essentially all distances will be in focus. But with a wide aperture, like f 1.4 for example, the depth of field will be short (less than 1 foot). So if you focus on your subject with an f 1.4 aperture setting, then things at other distances will be out of focus. The degree of "out of focus" depends on the aperture that you select. Of course, selecting a wider aperture means that the shutter speed has to be increased (shutter open time shortened) so that the same amount of light will fall on the film for proper exposure, as appropriate for the film speed that you are using.
