Shutter Speed vs. Focal Length Rule for Razor Sharp Photos

Shutter Speed vs. Focal Length

There are few things that can drive a photographer crazy; one of them is when your images are not being as sharp as you need them. In some cases, you've done everything that is needed to be done and yet the images continue to fall short. You may think it is because of the camera shake, so you end up getting a new tripod but it doesn't solve the problem.

If your images are not sharp as you expect them to be and you've tried every other thing without success, the culprit may be the shutter speed and focal length. In this case, you will need to master the shutter speed vs. focal length rule and no camera shake if you are hoping to get razor sharp photos.

Your images can suffer from camera shake even without your notice. Sometimes when you hit the shutter button, there will be a tiny camera shake which may be invisible to you but the camera will still register such small movement. Any type of camera shake can ruin things for you.

One reason why even the smallest camera shake can cause a problem for you is because of the relationship between the shutter speed and the focal length of the lens and we are going to take a good look at this rule of thumb below.

Rule of Thumb for Shutter Speed and Focal Length

Minimum Shutter Speed (sec) = 1/Focal Length (mm)

So far we've been talking how this works in theory, let's take a look at how it works in real life. Imagine you take a shot at a focal length of 50mm; the shutter speed of your camera must be 1/50 sec and even faster in some cases. If this is true, and you zoom to say 200mm so you can avoid camera shake and get a razor sharp image, you will need to keep the shutter speed at least 1/200 or faster.

How to Determine The Focal Length to Use

Most amateur photographers think that it is hard to determine focal length but it is actually very easy. To determine the focal length to use, take a look at the number aligned with the small line marked on the top of your lens. The focal length changes as you zoom out and you may need to adjust the shutter speed accordingly due to the changes. If you have your focal length set at 70mm, you will need a shutter speed of 1/80 or even higher in order to get razor sharp images. On the other hand, a focal length of 300mm on a large zoom will require the shutter speed to be at least 1/300 or higher.

Note that if you are using a prime lens, you will need to match the shutter speed to that specific focal length so you can avoid any camera shake.

This rule above is ideal when you are using classic 35mm film cameras and full-frame digital cameras. However, due to the recent introduction of APS-C sensor, there may be some modifications to this rule of thumb and it is stated below:

Minimum Shutter Speed (sec) = 1/Focal Length (mm) x 2

Due to the fact that most of the DSLR cameras coming out today have a cropped sensor (you can check the camera's specifications to be sure), you will need to multiply the focal length by 2 when you are calculating the "safe" minimum shutter speed. Let's take for instance; if you have 60mm as your focal length, your shutter speed should be 1/25 sec or faster.

Key Points to Keep in Mind

The following points are important when you want to get razor sharp images:

  • Find out the "safe" shutter speed of all your lenses. You can easily do this by matching the maximum focal length of your lens to a shutter speed and make sure you have that in mind when you are using each lens. For instance, you will need to use a shutter speed of 1/200 or faster if the focal length of your lens ranges from 70mm to 200mm irrespective of whether you zoom in or out.
  • If you are not using a tripod, you can use 1/30 sec which is the slowest shutter speed that allows the camera to keep steady. The general rule is not to go slower than 1/30sec even if your lens is 18-55mm and you zoom out to 18mm. This will help you avoid camera shake.
  • Keep your camera as steady as you can if you have to go below the minimum shutter speed because there is not enough light available. You can do this by leaning against a solid object, gripping the camera well with your right hand and then using the left hand to support the weight of your lens. Finally, press your elbows against your body, and press the release button while holding your breath.
  • If your shutter speed is slower than it is supposed to be; try to take many shots at once. If you are lucky, some of the images will be sharper than others.


Note that it may take time before you master this rule of thumb for shutter speed vs. focal length. It will take practice and consistency, but over time, you will get good at it.

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