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True as far as it goes..
In the scenario described, Depth of Field is virtually the same for both focal lengths. All other factors being equal (except for focal length), and the longer focal length has the shorter depth of field. Put both cameras at the SAME distance from the subject, enlarge the image from the shorter lens to match image size to the longer lens and the depth of field for the longer lens will be shallower compared to the shorter lens (perspective will be different as well).
Lens focal length DOES affect DOF
DOF is determined by lens aperture, lens focal length, distance to the subject and (to a significantly lesser degree) the acceptable circle of confusion. In fact, DOF is often stated as being computed from lens aperture and subject magnification (on the film/sensor). Subject magnification is determined by lens focal length and distance to the subject. Since Mr. Long changed *two* of the above factors (lens focal length as well as distance) to maintain the same subject size, he would, in fact, end up with the same depth of field. If he had taken an image of the roof vent with the longer lens from the same position as with the shorter lens, the DOF would have been significantly reduced.
Also note that film/sensor size does *not* directly affect DOF. With a smaller capture medium you must use shorter lenses from the same distance in order to capture the same image. The shorter lenses result in greater DOF - not the smaller sensor.
Richard Baker
Sunnyvale, CA
Maybe I just haven't been paying attention,
but in 25 years of photography I don't remember ever being taught, or even hearing, that DOF is related to focal length. It's always been clear to me that DOF is related to aperture and film size (film now being sensor size). Who's been teaching you?
By the way, I would prefer white cameras if Nikon and Leica made them. Less heat in the sun. Black is "more professional" because it doesn't reflect in the sun, calling more attention to the camera than necessary.
And it's definitely not true that the best shots present themselves when you don't have a camera with you. The truth is that the best shoots are always ruined by the rare foul-ups that plague photography, such as film streaks or mechanical shutter failure and the like!