Nikon D7000 manual DOF in Depth

366 David Busch’s Nikon D7000 Guide to Digital SLR Photography

Table 11.1 turns the conventional “equivalent” listing on its head. Usually, you’ll see a table that tells you that, say, a 100mm lens when used on a camera like the Nikon D7000, will have an equivalent field of view of a 150mm lens on a full-frame camera. That’s actually not a difficult calculation, and might not be as useful as you think. If you’re concerned about focal length equivalents, you probably have some experience using full-frame cameras.

So, what you really want to know is, if I want the same field-of-view that I got with my old 20mm lens on my film camera, what focal length lens do I need to use now? The fact that your 20mm lens is now the equivalent of a 30mm lens on the D7000 isn’t as important as the question, “Do I own a lens that will provide the same field of view that I used to get with my trusty 20mm lens?” That’s what the table shows you. In the center column, you find a list of common focal lengths for prime lenses originally designed for full-frame cameras. You can scan down the column to see that, if you want the same field of view that you got with your 35mm lens, you’ll need to use a 23mm focal length or zoom position when you’re shooting with the D7000. Or, if you preferred 85mm as a focal length for portraits, that you’ll need a 56mm focal length when the 1.5X crop factor is figured in. The left column shows the angle of the field of view of each lens’s focal length, because many old-timers sometimes think in those terms.

The crop factor strikes again! You can see from this table that wide-angle lenses provide a broader field of view, and that, because of the D7000’s 1.5X crop factor, lenses must have a shorter focal length to provide the same field of view. If you like working with a 28mm lens with your full-frame camera, you’ll need a 19mm lens for your Nikon D7000 to get the same field of view. (Some focal lengths have been rounded slightly for simplification.)

DOF IN DEPTH

The DOF advantage of wide-angle lenses is diminished when you enlarge your picture; believe it or not, a wide-angle image enlarged and cropped to provide the same subject size as a telephoto shot would have the same depth-of-field. Try it: take a wide-angle photo of a friend from a fair distance, and then zoom in to duplicate the picture in a tele- photo image. Then, enlarge the wide shot so your friend is the same size in both. The wide photo will have the same depth-of-field (and will have much less detail, too).