Shutter Speed Makes Sharp Images

The sharpest images come from a completely still camera. However, when we are on vacation, we sometimes visit locations where tripods are not allowed. Or we don't want to infringe on our companions' experience by carrying a tripod everywhere. That's when knowing a simple math formula can help you get a sharp shot.

1/125 second, 18-55mm lens, APS sensor camera, hand-held

The traditional formula (based on 35mm film cameras) for a sharp hand-held photograph is to take the length of your lens and put a 1 over it. The resulting fraction is the slowest shutter speed you should use to ensure an acceptably sharp image without blur from camera shake. For example, if you have a 50mm lens, putting a one over the 50 equals 1/50 second for the shutter speed.

  • 1 / lens length = full-frame hand-held shutter speed 
  • 50mm lens
  • 1/50 second =  full-frame hand-held shutter speed 

This formula works fine if you are using a fixed (prime) lens on a full-frame camera. But what if you have a zoom lens? Or what if your camera has an APS or Four-Thirds sensor instead of full frame? Don't panic!

First, use the long end of your zoom lens for the formula. In a common 18-55mm kit lens, use 55 for the formula. Second, multiply this lens length by two, making 110. Putting a 1 over it would give you a shutter speed of 1/110 of a second, but cameras don't have this choice. Instead go for the next faster shutter speed, in this case, 1/125 second.

  • 1 / (lens length x 2) = APS hand-held shutter speed  
  • 18-55mm lens
  • 55mm x 2 = 110
  • 1/110 not available
  • 1/125 second = APS hand-held shutter speed

So if you are using an 18-55mm zoom lens on an APS or Four-Thirds model camera, the slowest hand-held shutter speed you should use to prevent blur from camera shake is 1/125 second.

Learn more tips for sharp, hand-held pictures in my one-day Getting to Know Your Digital SLR Camera class on June 9, 2018, in Missoula, Montana. Click here to register online.