Today’s Question: With reference to your answer about a rule for minimum shutter speed relative to lens focal length, how does the presence of image stabilization in the lens impact this? In other words, can’t I use a slower than recommended shutter speed when employing image stabilization?
Tim’s Quick Answer: Image stabilization technology does provide a benefit that could enable you to employ a slower shutter speed (longer exposure duration) than would otherwise be possible when shooting hand-held (and even when shooting on a tripod in many cases). However, my preference is to treat this benefit as a “bonus” and to continue following the rule of thumb about minimum shutter speed relative to focal length.
More Detail: As a reminder, the rule of thumb about minimum shutter speed relates to lens focal length. More accurately, this rule relates to field of view. With a narrower field of view, any movement of the camera will essentially be magnified, requiring a faster shutter speed to ensure a sharp image. As a general guideline, it is recommended that the lens focal length be used as a minimum value for the denominator in the shutter speed. So, a 100mm lens would call for a 1/100th of a second or faster shutter speed, and a 300mm lens would call for a 1/300th of a second or faster shutter speed.
Image stabilization technology is generally promoted as providing a benefit expressed as a number of stops of light. You might achieve a benefit of anywhere from one stop to about five stops, at least according to marketing materials from various manufacturers. For illustrative purposes, let’s assume a two-stop benefit from a given image stabilization technology.
With a two-stop benefit you could use a slower shutter speed than would otherwise be possible. So with a 100mm lens you could use a 1/25th of a second shutter speed rather than 1/100th of a second. With a 300mm lens you could use a 1/75th of a second shutter speed rather than 1/300th.
While I certainly appreciate the benefit of image stabilization technology, I also realize there are limitations and a variety of other real-world issues that may affect the sharpness of my photos. Therefore, I prefer to follow the rule of thumb about shutter speeds relative to focal length without taking image stabilization into account.
As a result, any benefit caused by image stabilization becomes a “bonus” benefit, further increasing the chances of capturing a sharp photo when shooting hand-held.