Safe Shutter Speed

[Originally posted on 6/8/2019]

Camera shake, if not the only one, might be the number one reason for producing blurry pictures. 

Camera shake normally comes from the unsteady hands. However, the “unsteady hands” can be a relative concept. When the shutter speed is high (e.g. 1/800 sec) then the shake introduced by your hands might not be significant. On the other hand, when your shutter speed is low (e.g. 1/30 sec), then many of us can not survive the camera shake.

Can we see the camera shake before we take the picture? Yes, we can. When you look through your view finder, after you acquire the focus (normally you see something green is lit in your view finder), hold the camera a bit longer and you will start to see your focus going around the object you originally put your focus on. So once you acquire the focus, you want to keep the objects in your viewfinder steady and complete the shot as soon as possible. When you have a longer shutter speed, it adds time to the process and let your unsteadiness have a chance to creep into it.

In short, in order to keep your picture sharp, you don’t want to use the low shutter speed. But how low is too low? For normal people, 1/60 sec is the limit. With the shutter speeds lower than that, you are in the danger of having blurry pictures.

But 1/60 sec is just a general rule. If you can, pick up a 300mm lens and try to acquire the focus and you will see the image in your view finder might never stand still. The longer the lens, the harder to avoid the camera shake. This is geometry, let me know if I need to explain more on this. So 1/60 sec will never be fast enough for a 300mm lens.

We finally come to the term “safe shutter speed”. So the rule of thumb is if you have a lens with focal length of f, then your safe shutter speed is 1/f. That means, with a 300mm lens, your safe shutter speed should be at least 1/300 sec. For non-full frame system (e.g. APS-C or m43), the crop factor plays a trick in this concept. Take m43 system as an example, the crop factor is 2. If I have a 300 mm lens then its full frame equivalent focal length becomes 600mm so the safe shutter speed becomes 1/600 sec. For those of you who have Canon APS-C cameras (e.g. Rebel line), the crop factor is 1.6 and for Nikon, the APS-C crop factor is 1.5 so the safe speed will be 1/480 sec and 1/450 sec relatively.

By the way, the big names like Canon, Nikon, and Sony all introduce their own technologies to help the users to avoid the camera shake, the so called anti-shake system. Some implement that on the lens (e.g. Canon’s IS and Nikon’s VR) and some (e.g. Sony and Olympus) implement it on the sensor, the so called IBIS (In-Body-Image-Stabilization). Some of them are very efficient and can help to produce sharp pictures couple stops lower than the safe shutter speed. There are cases that you need to use the super low shutter speed (e.g. night scene). For those cases, using a tripod will be your only solution!