The Shutter Speed “Rule of Thumb” for Handheld Shots

Another common question that has been asked of me usually relates to blurry images, as a matter of fact it comes most frequently when amateur and hobbyist photographers shoot indoors with a telephoto lens. And here it comes, “My images are much more clear with the kit lens than my expensive telephoto when I am indoors, my telephoto must be defective.”

Your telephoto lens isn’t defective, there is just a rule that is rarely taught anymore in the age of digital, and most people simply say, “Just use your tripod.” and it will be better. In most cases it will be better, but it isn’t always necessary.  The inverse shutter speed rule for handheld photography is designed around traditional film SLRs which have no crop factor like many of todays D-SLRs, in other words; unless you are using a full frame D-SLR, you will have to do some math.

The rule states: When shooting handheld in natural light, one should never shoot at a shutter speed slower than the inverse of the desired focal length.

At times the person I am explaining this to is an engineer and they simply reply, “OK” and walk away. For those of us that don’t design jet engines, there is explanation required.  So, what it means is simply this: if you are outdoors and shooting a focal length of 100 mm (D-SLR users must do the math for their crop factor; e.g. A 1.6x crop factor camera will show 62.5 mm and be at a real focal length of 100 mm), you should never shoot a shutter speed slower than 1/100th of a second.

Sometimes you will be in a situation where there is not the luxury of directly matching numbers, for example if you have a 17-40 mm wide angle lens set at 17 mm, there is no 1/17th of a second shutter speed. In these situations it is always best to round up (sorry, more math) to the next fastest shutter speed. In the case of our 17 mm scenario, your lowest handheld shutter speed should be 1/20th of a second. (17 mm on a 1.6x crop factor body is actually 27.2 mm, and should therefor be shot at 1/30th of a second or faster.)

This is very basic high school physics in action, if you remember the principles of levers and fulcrums. When a lever is placed on a fulcrum at the center, the two end points of the lever will move the same distance when force is applied. When you slide the lever to one side and apply force to the short end, the long end moves a much greater distance. When you twitch and your camera is set to 17 mm, the lens element farthest from the film plane moves much less than when the same twitch is applied at 300 mm. (when at 300 mm, never shoot slower than 1/300th of a second and do the math if you are using a D-SLR with a crop factor.)

The only time when this rule can be mildly bent, is when using Image Stabilized lenses. In the case of image stabilized lenses, I will never suggest pushing it to the limit of the IS, instead try breaking the rule by 1 ƒ-stop instead of 3 ƒ-stops.

Happy Shooting!

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