1/f | Photocrati

Handholding: Making Sense of the 1/f rule

Polar Bear Walking. Without familiarity with the 1/f rule and how to use it, this 300mm shot would have been a blur. — Polar Bear Walking. Without familiarity with the 1/f rule and how to use it, this dusky 300mm shot would have been a blur.

I got some questions over the weekend about the details of the 1/f rule and I thought I’d share some of my answers with you. It is a simple formula which allows photographers to roughly estimate how fast a shutter speed they’ll need to prevent camera motion from blurring an image.

The “1/f rule” simply says that the longest shutter speed you can handhold a 35mm camera, with careful technique but without a tripod or other support, without getting blur from camera motion is about one second divided by the focal length of the lens (in millimeters). For a 100mm lens, the rule suggests that you’d have a shot at getting a sharp handheld shot at 1/100 of a second (or a 1/1000), but not a 1/10, or 1/50. This is fairly intuitive. Telephoto lenses magnify more, magnify motion more, than wide-angle lenses, and so you need a proportionally faster shutter speed to get a sharp image with the longer lens.

The rule is not particularly precise, though, and it is helpful to keep a few caveats in mind. (more…)