Blurry images are the bane of a photographer’s existence. I’ve yet to meet a photographer who has ever stated anything even remotely resembling the following:
“After spending a day out with my camera, I don’t mind unloading my memory card and discovering that 75% of my photos are blurry.”
Nope. Never. Unless you intend a shot to be blurry for some artistic reason, blur is something everyone tries desperately to avoid and rightfully so, as this can easily render a perfectly composed shot of your ideal subject useless.
Photo by James
If you’ve been struggling with blurry images and don’t know what to do about it, there is a relatively uncomplicated solution to your problem that won’t require you to dip into your bank account or carry around any extra gear. But before we get to that, let’s take a quick look at the most common culprit of blurry images: camera shake.
The Impact of Camera Shake
There are a few different factors that might cause your photos to come out blurry, including missed focus or a dirty or damaged lens, but more often than not the problem is camera shake. This refers to the blur that is introduced via camera movement — however slight — during the making of an exposure. It can be particularly troublesome at slower shutter speeds and longer focal lengths as the human hand simply can’t be held perfectly still.
Photo by ozz13x
Imagine trying to hold a 1-foot wooden rod out in front of you. Now imagine trying to do the same with a 10-foot rod. Which do you think will shake more violently in your hand?If we apply this principle to photography, with the length of the wooden rod being analogous to a lens’ focal length, it’s a bit easier to see why it’s more difficult to get successful hand held shots at longer focal lengths. Just as longer focal lengths increase subject magnification, so do they exacerbate the effects of vibrations transmitted by your hands. The only way to overcome this is to increase your shutter speed. However, you can’t just use some randomly selected shutter speed as long as it’s faster than what you tried previously; there’s a method to it and there’s some math involved, but it is really quite simple to determine the right shutter speed to prevent camera shake.
The Reciprocal Rule
You may find this rule disguised in other names (“the law of reciprocity,” for example) but they all mean the same thing and work the same way:
When you are hand holding your camera and you want to ensure that your images come out free of camera shake, whatever focal length you are using should serve as the lower limit for your shutter speed. As an example, if you are using a 100mm lens, your shutter speed should be at least 1/100th of a second. Using a zoom lens set to 250mm? Set your shutter speed to 1/250th of second or faster. Easy, right? Yes, but there is an important caveat to consider. This specific implementation of the reciprocal rule applies only to full frame DSLRs (or 35mm cameras).
Photo by James Russo
In order to adapt the reciprocal rule to crop sensor cameras (APS-C, 4/3rds, APS-H, etc.), you have to account for the camera’s crop factor by multiplying the crop factor by the lens focal length. If, for instance, you are using a focal length of 100mm on a camera with a crop factor of 1.5x (commonly used by Nikon, Sony, Samsung, and Fuji APS-C cameras) you will need to set a minimum shutter speed of 1/160th of a second (100 x 1.5 = 150, but you won’t find 1/150th on your camera so go up to 1/160th). Using a camera with a crop factor of 1.6x (the current Canon APS-C standard) and a focal length of 100mm will yield a minimum shutter speed of 1/160th of a second (no need to round up this time).
Photo by Santiago Atienza
Although this is referred to as a “rule,” remember that rules can and often should be broken. All this talk of reciprocals should be taken as more of a handy guideline to help you minimize camera shake. The rule isn’t totally fool-proof, and it’s a good idea to err on the side of speed; if, by applying the reciprocal rule, you determine you need a shutter speed of 1/80th of a second, don’t hesitate to shoot at 1/100th of a second.
Photo by Julie V.
There you have it. When you can’t or don’t want to carry a tripod or if you don’t own a lens or camera with image stabilization, you still have a reliable means of avoiding the crushing disappointment of blurry shots. Good technique + the reciprocal rule = blur-free photos.
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