Most people shoot their cameras hand-held. Even professional photographers rarely bring a tripod everywhere. So one of the biggest challenges of hand-held photography is yielding sharp images. Especially when using zoom or telephoto lenses. Most beginners and some intermediate hobby photographers struggle to understand the source of this problem. The main cause is camera shake.

The Reciprocal Rule will help you yield sharp photos when you shoot hand-held.

The human body cannot stay completely still for long periods. This is especially true when holding something like a camera in our hands. So when we take pictures while hand-holding a camera, the micro-movements of our body introduce unwanted blur to our photos. That is why we use the Reciprocal Rule to avoid said blur.

Unfortunately, the Reciprocal Rule is often misunderstood. For example, the “greater half” of “photographers” may say something like this:

The camera shutter is a curtain that stays closed until you fully press the shutter button. At that point, the curtain opens and exposes the camera sensor to the light passing through the lens. The curtain closes after a specific exposure time, and the light stops hitting the sensor. Therefore, slower shutter speeds allow the sensor to gather more light, and the image will be brighter. Conversely, faster shutter speeds allow less light to hit the sensor, and the resulting image will be darker.

The shutter speed is the time between the opening and the closing of the curtain. It is one of the ways that we use to control the amount of light that hits the sensor. If the shutter speed you choose is too fast or too slow, the image may not be properly exposed.

While the curtain is open, the camera sensor records all the light passing through the lens. Therefore, when the shutter speed is low (the curtain stays open for longer), the moving subjects in the frame will be blurry. Slower shutter speeds can be used intentionally as a tool for artistic expression in certain situations and have a tripod on hand. However, if you hand-hold the camera, you can introduce camera shake to your pictures.

We measure shutter speeds in seconds or fractions of a second. For example, the slowest shutter speed I feel comfortable shooting without introducing much blur due to camera movement is about 1/125 (one-hundred-and-twenty-fifth) of a second or about eight milliseconds.

Some cameras can handle faster speeds like 1/4000th or even 1/8000th of a second and faster. However, there is a limit to how quickly the curtain can open and close. The lower speeds on the other end of the spectrum typically go up to 30 seconds. So you can use even longer shutter speeds when you set your camera to Bulb if the situation requires it.

There are, of course, a few exceptions. An example is leaf shutter lenses, where the shutter speed is a component of the lens. Such lenses are mainly used with medium format cameras, and here I will only address full-frame and crop sensor cameras.

So how does all this relates to camera shake?

To quote Severus Snape, the causes for camera shake like “The Dark Arts are many, varied, ever-changing and eternal.” It can be something as basic as shaking hands, improper hand-holding, or vibrations caused by the camera shutter and mirror (if you have not gone mirrorless). Yet, the most common reason for your hand-held pictures to be blurry is simple and easily remedied. The answer is too low shutter speed, or should I say lower-than-acceptable.

Hence, any change in the position of a point resulting from camera motion (shake) is amplified when using a long focal length lens. Combine that with the narrower Angle of View, and a seemingly imperceptible camera movement may result in a noticeable image blur.

Now imagine paying $2,799 for a Canon RF 70-200mm L/2.8L IS USM lens to pair with your Canon EOS R full-frame body. It is a fantastic, fast telephoto lens with excellent zoom capabilities. However, when you start shooting with it, you have to remember a couple of things. First, the lens’s focal length will change when you zoom in. Therefore, the Angle of View (which in this case is the same as the Field of View of the lens) will go from 34° (degrees) at 70mm to 12° (degrees) at 200mm (according to Canon’s lens’ specs). So if the 70mm lens has a 100m diagonal Angle of View, the 200mm lens will have a 35m Diagonal Angle of View. Then if the subject moves 1m, it will be a 1% change across the shorter lens’ field of view but approximately 3% change across the longer lens’ field of view.

The combination of a longer focal length and a narrower Angle of View is that a slight change in the camera orientation will result in a blurry image. If you have such a lens, you have probably noticed that looking through the viewfinder may be a bit nauseating when you are zoomed in to the maximum. The reason is that camera movement is magnified when you use lenses with longer focal lengths.

As you already know, blur can be a useful artistic tool, when applied intentionally. However, tons of images are ruined by unintentional. To avoid it at longer focal lengths while hand-holding the camera, you must adjust your shutter speed to freeze the frame. The Reciprocal Rule is a guideline established during the days of the film camera. It gives a decent starting point as to the shutter speed you need to use to avoid the result of camera shake.

If you employ a decent hand-holding technique, the Reciprocal Rule suggests that your base shutter speed should be one over the focal length. So, when shooting at 100mm, you should consider a minimum shutter speed of 1/100th of a second.

On the other hand, if you hold the camera incorrectly, you may need to increase the shutter speed even more to counteract camera shake. Weather conditions and equipment weight can also affect camera shake. If you are shooting outside in very windy conditions, your whole body may be moving slightly. When using a heavier setup, your hands will get tired faster, which will result in camera shake. If you aspire to be a wildlife photographer or sports photographer, you check out the article on Photographing Hand-Held with Telephoto Lenses by Thomas Stirr.

Keep in mind the Equivalent Focal Length which depends on whether you are using a full-frame lens on a crop sensor body. If you do, you will need to multiply the sensor’s crop factor by the lens’s focal length to determine your minimum recommended shutter speed.

Look at your lens and see if it has image stabilization — IS (also known as vibration reduction — VR). If it does, you have a bit of leeway with the shutter speed. IS/VR reduces camera shake in a couple of ways. IBIS (in-body stabilization) physically moves the sensor to compensate for camera movement. Most newer lenses have IS/VR built-in, where some of the elements inside the lens move to reduce shake.

Find out how many stops your lens is rated for (usually 2–4 for Canon and Nikon lenses), and you can reduce your shutter speed by ½ for each stop of stabilization. I prefer to stick to the Reciprocal Rule even when I use stabilized lenses and lower my shutter speed only if absolutely necessary.

You may have to consider the resolution of your camera sensor when picking the shutter speed at which you are shooting. Pictures taken with higher resolution camera sensors are more susceptible to blur due to camera shake. The more pixels you cram in the same physical space, the more likely the images are not sharp at 100% zoom. To compensate for a high-resolution sensor, you may need to increase the shutter speed.

To get tac sharp images, you will need not only high shutter speed but good quality glass. This is even more important if you are using a high-resolution camera.

If you are trying to take a picture of a tiny subject at a very long distance, you will need to dramatically increase the shutter speed if you want to see sharp details at 100% zoom.

Things are great when you can or want to use equal or faster than the “minimum” shutter speed. But what happens when it is too dark and you cannot use fast shutter speeds? You can do a couple of things, but you need to remember that “There is no free lunch.”

One thing you can do is to increase the aperture to let in more light. If you are lucky enough to have a lens like the Canon RF 70-200mm L/2.8L IS USM, you can probably do that, but if you only have the Canon EF 70-300mm f/4-5.6 IS II USM, you are not that lucky. Plus, opening the aperture too much at longer focal lengths may create some issues with focus hunting.

Another thing you can do is play with the ISO. To compensate for low light, you can up the ISO and keep the same aperture and shutter speed. However, this will introduce more noise to your photo.