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Shutter Speed vs. Focal Length Rule for Razor Sharp Photos

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Have you ever wondered why some of your images are not as sharp as they should be? Or have you noticed that the more you zoom in with that nice new lens of yours, the trickier it is to get sharp images? If the answer is yes, then you definitely need to master shutter speed vs. focal length rule for those razor sharp photos and no more camera shake! It may sound more complicated than it really is, so let's see how that rule of thumb works...

Lack of sharpness in the photos of still subjects is usually to be blamed on what is called camera shake. In other words, you may accidentally shake the camera while pressing the shutter release button. You may not even feel it or see it on the camera screen, but the camera will register that tiny movement and the details in your image (when enlarged on computer screen) will not be as crisp as you would like them to be. This is what camera shake looks like in the image:

Camera shake
1/13 sec, 50 mm
Camera shake
1/13 sec, 50 mm (the details are far from being as sharp as they could be)

The quick and simple explanation is that there is direct relationship between the shutter speed and the focal length of the lens. Let's not get technical and simply say that to avoid this type of problem, we need to apply the Shutter speed vs. Focal length rule of thumb:

Shutter speed rule 1

Here's how it works in practice: if I take a photo at a focal length of 50 mm, the shutter speed on my camera must be be 1/50 sec or faster. Following the same logic, if I zoom in to 200 mm, to avoid any camera shake and achieve a perfectly sharp image, the shutter speed must at least be 1/200 or faster. 

If you compare the camera settings for the image above and below, you will notice that the shutter faster speed was better suited for the focal range, resulting image is perfectly sharp:

Sharp image
1/50 sec, 50 mm
Sharp image
1/50 sec, 50 mm (detail)

Determining the focal length is easy: look at the number aligned with the small line marked on the top of your lens. As you zoom in or out, the focal length changes and you need to adjust the shutter speed accordingly. A focal length set on 70 will require a shutter speed of 1/80 or higher to get sharp images; for a focal length of 300 on a large zoom, the shutter speed should be - you guessed it - 1/300 or higher.

 If you have a fixed focal length lens - also called prime lens - then you only need to match the shutter speed to that specific focal length to avoid any camera shake. 

Lens

This rule of thumb works perfectly well for classic 35 mm film cameras and full frame digital cameras. However, with the introduction of lighter, smaller and more affordable cropped sensor digital cameras (or APS-C sensor), the rule of thumb needs to be slightly changed and looks like this:

Shutter speed rule 2

Since the majority of prosumer DSLR cameras have a cropped sensor (if you are not sure, check your camera specifications), when calculating your "safe" minimum shutter speed, simply multiply the focal length by 2. For example, if your focal length is 60 mm, then the shutter speed will have to be 1/125 sec or faster.

Points to remember:

  • To keep it simple, find out what is the "safe" shutter speed for each of your lenses. To do that, match the maximum focal length of your lens to a shutter speed and keep that in mind at all times when using that lens. For example, if the focal length of your lens ranges from 70 mm to 200 mm, use the shutter speed of 1/200 sec or faster regardless whether you zoom in or out.
  • When photographing handheld, the slowest shutter speed that allows to keep the camera steady for most people is 1/30 sec (unless you are a surgeon with a very steady hand). Therefore, even if your lens is 18-55 mm and you zoom out to 18 mm, try not to go slower than 1/30 sec to avoid the camera shake.
  • If there is not enough available light and you have to go below the minimum shutter speed, make sure to keep the camera as steady as you can. To do that, lean against a solid object, grip well onto the camera with your right hand and use the left hand to support the weight of the lens, press your elbows against your body, and hold your breath when pressing the release button.
  • When your shutter speed is slower than it should be, take a few photos at once: some of them will turn out sharper than others.

Now it's time for practice! Get your lenses, check their focal length and experiment with various shutter speed settings. We look forward to seeing your results!

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About the Author

Nadia Gric

Nadia Gric

Nadia is passionate about the visual aspect of life and the personalities she meets along the way. Living in the heart of Paris, Nadia never stops exploring the City of Light through her camera and readily shares her knowledge and love for photography. Learn more...