Mounting an L-Bracket to a Fluid Video Tripod Head
The solution your looking for is a nodal slide rail. Continue reading for more specific details on the problem and the solution.
The Problem
Fluid video tripod heads have their plates orientated such that the rails of the plate run in the same plane as the tilt mechanism of the tripod head. So, to tilt your camera up/down, you mount the plate to your camera so that the rails run front-to-back (i.e. in-line with the optical axis of the lens). This design choice was made because video camera systems are usually long and heavy, and so it is assumed that users looking to attach a mounting plate to a long and heavy system would do so such that the mounting plate would run along the longest dimension of the system, thus offering maximal support for the heavy weight. This turns out to be in-line with the optical axis of the lens, hence, the design of fluid video tripod heads and why telephoto lenses always have their mounting plates running along their optical axis.
However, a problem arises when you cannot, or do not want to, mount the
bracket to your camera in this manner, for example, when needing or wanting
to use your camera's L-bracket. In such a scenario, the rails of the
L-bracket run perpendicular to the optical axis of the lens. Thus, the
tripod head tilt mechanism no longer works as desired up/down, but instead
left/right
. In more technical and unambiguous terms, the tilt
mechanism no longer works to adjust the pitch of the camera as desired, but
instead adjusts the roll of the camera.
The Solution
The solution is to use nodal slide rail (also known simply as a
nodal slide
, or a nodal rail
) in-place of the standard
mounting plate provided with your fluid video tripod head.
A nodal slide rail is a rail that allows one to slide the position of a camera forward and backwards, thereby enabling one to position a nodal point of the camera lens in a particular position.
Adjusting the position of a nodal point may be done for a variety of reasons, for example: focusing in macro-photography, avoiding parallax error in panoramic-photography[1], or adjusting the counter-balance point on a fluid video tripod head. In our case, the nodal slide rail simply allows one to mount an L-bracket to the fluid video tripod head in an orientation that allows the tilt mechanism of the tripod head to tilt the camera up/down (i.e. adjust pitch) instead of left/right (i.e. adjusting roll).
[1] There is a common misconception about there being a
single nodal point in a camera lens, and that this point is at the
iris diaphragm, and is the correct pivot point so as to avoid
parallax error in
panoramic-photography. This is incorrect. Rather, there are two nodal points
along an optical axis, the position of these points is dependent on the
optical system (lens), and the correct
pivot point is the
entrance pupil
(physical aperture) of the lens.