WHAT IS THE REFERENCE RULE IN A PHOTO?
Do you know how to take clear photos without using a tripod? Many get blurry images, often associated with camera shake when the shutter is released. Unfortunately, this can also occur due to the incorrect position of the hands on the camera, and from shutter vibrations, which can cause serious difficulties or even become an unsolvable problem.
This article will discuss the most common reason for camera shake: the shutter speed is below acceptable when manually holding the camera. Photographer Nazim Mansurov (Nazim Mansurov) explains in simple terms an empirical inverse rule that can significantly increase the chances of getting clear photographs if you do not have a tripod at hand.
What is the reverse rule in photos?
A picture taken while holding the camera with your hands is the opposite. Sony A7R + FE 35mm f / 2.8 ZA @ 35mm, ISO 100, 1/40, f / 11
Due to the fact that we, the people, cannot physically be absolutely still, especially when we hold something weighty in our hands, our movements can cause camera shake and eventually result in blurring of images. The basic premise of the reverse rule is that the shutter speed of your camera should be at least inversely proportional to the effective focal length of the lens. This is easy to understand by example.
Let’s say you’re shooting with a zoom lens on a full-frame camera. The rule is: if you photograph at 80 mm, your shutter speed should be set to at least 1/80 second, whereas if you use an approximation of, say, 400 mm, your shutter speed should be at least 1/400 second. Using such fast shutter speeds should prevent blurring when camera shake. Why so?
Since there is a direct correlation between focal length and camera shake, the longer the focal length, the greater the likelihood of camera shake. If you use a telephoto lens, you probably already noticed how the viewfinder shakes as you increase the focal length compared to the shortest. This happens because the camera movement increases at longer focal lengths.
What is the reverse rule in photos?
The red dotted lines, representing the potential limit of how the camera can shake when held in the hands, have a much smaller sweep at 80 mm than at 400 mm. This is because camera shake increases with increasing focal length.
Blur due to camera shake – this is NOT a blur due to the movement of an object.
It is important to note that the blur caused by camera shake is very different from blur from motion (when the object is faster than the specified shutter speed) – this is usually a blur of the WHOLE image, while the motion blur has only an object or part of it, the rest is looks sharp. It is also important to note that the reverse rule is applicable only when the camera is held by hands – if it is mounted on a stable support, then such fast exposures are not required.
If you have a camera with a sensor smaller than 35 mm / full frame (and most entry-level SLR cameras and smaller mirrorless sensors), you must first calculate the effective focal length, also known as the “equivalent field of view”, by multiplying the focal length on the crop factor. Therefore, if you use, for example, an 80–400 mm lens on a camera with a framing factor of 1.5x and shoot at 400 mm, the minimum shutter speed should be at least 1/600 second (400×1.5 = 600).
Notes and Exceptions
Although this rule is usually referred to as “reverse”, it is not in itself a rule – it is just an indication of the minimum shutter speed to avoid blurring due to camera shake.
It should be remembered that the shutter speed affects camera shake from a number of different variables.
The effectiveness of how you hold your hands on the camera: if you have a bad technique, the rule of reciprocity may not work, and you may still have to use higher shutter speeds. Equipment and lenses vary in size, weight and size, so you may need to use special techniques, depending on what you are shooting.
Camera resolution: whether we like it or not, the resolution of digital cameras increases, and an increase in the number of pixels placed in the same physical space can greatly affect how sharp the images are at 100% magnification. Higher resolution cameras will noticeably suffer less camera shake than their lower resolution counterparts.