A tripod holds a camera still while the shutter is open, preventing motion blur. The tripod must be able to maintain this stability in the presence of uneven ground, wind, ground vibrations, etc. Generally, tripods are most easily characterized in terms of the size (weight and height) and maximum load it can support. Usually, heavier tripods are more stable and can support more weight than lighter tripods, but lighter tripods may be more suitable for backpacking or other situations where excessive weight is a concern. At the extreme, monopods and small ‘tabletop” tripods can be used when minimizing weight and volume is the most important consideration.
There are three parts to a tripod: the legs, the head, and the camera/lens mounting plate. Many tripods also have a ‘center column’ that can be used to raise the camera above the legs. The overall stability of a tripod is a function of the legs, while control of the orientation of the camera is provided by the head. The height of the camera is controlled both by the legs and center column.
“all in one” tripods consist of legs, head, and mounting plate integrated into a single device.
Legs generally consist of 3 or 4 telescoping tubes, and the most important properties are 1) the maximum diameter of the tube, 2) the number of leg segments, and 3) the construction material, The larger the diameter and fewer the number of segments, the more stable the tripod. Legs can either be opened to only a specific angle or can independently open to several angles, but it’s important to note that varying the leg angle only varies the camera height, not the tripod stability. Legs are typically aluminium, but carbon fiber can be used to provide additional benefits (vibration reduction, reduced weight, thermal insulation). Wood is also sometimes used. Telescoping segments are useful to both provide flexibility in camera height as well as correct for uneven terrain (for example, if the tripod is located on an inclined surface).
A center column allows for easier fine control of the height of the camera. Because the column introduces additional vibrational modes, for maximum stability the center column should not be raised. Additionally, the presence of a center column limits the *minimum* height achievable for tripods that allow legs to fully open- a feature that can be useful if the camera must be located near the floor or ground. A second benefit of tripods with no center column is the ability to orient the direction of view to vertical, by swinging the front leg of the tripod underneath and behind the head.
The head provides a mechanism to control the direction of view. Two classes of mechanisms- pan head and ball head- pivot the camera about a point below the optical axis of the camera, while a third class- gimbaled heads- pivot the camera about the center of mass, which provides additional stability when using heavy cameras. Pan heads provide separate control over each of the orthogonal rotation axes, while ball heads have a single mechanism (a captive ball and socket), which provides omnidirectional control. For both pan and ball mechanisms, the control and overall stability decrease as the lever arm between the center of mass of the camera and the point of rotation moves away from vertical. Often, ball heads will provide a “90 degree index” , which is a slot machined into the socket allowing either portrait orientation or vertical orientation, but the stability of the tripod is minimized and use of this index is not recommended. Because of this, it is generally recommended that “L-plates” be used for mounting the camera in portrait orientation. Gimbal mounts do not allow for rotation about the optical axis, although integrated lens mounts generally allow for this motion. Finally, there are several head attachments available for specialized operations: panoramic shooting sometimes requires precise camera rotation about the “no parallax” point, and macro shooting requires precise control over the object distance, and so translation and rotation stages are available which provide this specific control.
The mounting plate can either be a simple 1/4″ threaded post on the head into which the camera or lens directly attaches, or can consist of a “quick release plate”. Quick release plates provide an added measure of security/safety when attaching or removing a camera due to the simplified process of attachment. The mounting plate is first attached to the camera or lens, and the mounting plate is placed on the head and clamped into place. Individual manufacturers can make their own plates, or plates can be made in a “Arca type” or “Arca-Swiss” plate geometry which is considered a standard.
PhD Physics – Associate Professor
Department of Physics, Cleveland State University