The Torque Enemy in the Physics of Photography
Photography at its core is all about mastering and manipulating light. In science, light and its properties are defined and measured in the discipline of physics.
However, from an equipment point of view, there are other elements of physics that come into play in photography. Here in this post I look at Torque and its simple force to break equipment.
Torque is commonly understood as a rotational force – but is technically measured as the force applied to a lever.
Any time I experience an equipment failure, I try to understand how to prevent a recurrence or at least predict points of failure. The goal is to be able to either avoid (better) or at least quickly recover from them. More often than not, torque is the basis for the failure – and usually introduced by some failure on the part of the photographer.
Example 1: Nikon Battery Door Cover
The battery compartment cover has two obvious failure points, being the two small pins – they serve as the hinge which the cover swings open on.
As you can see in the photograph above, one of the pins broke, requiring a replacement cover.
In this case the torque was introduced in the studio equipment cage, and illustrates a workflow failure. I have always placed camera bodies on the rack with the battery compartment door open – to remind me to place a freshly charged battery into the body before use. That open battery compartment door invites torque to a level that the manufacturer never designed for in tolerances. When sliding the body onto the equipment rack with the battery door open, the pin broke when the door struck another camera body.
Postmortem: battery door covers always latched; a spare door cover for each camera body type in the equipment locker.
Note: the Nikon battery door cover will still latch with only one of the two battery door pins intact.
Example 2: Off Camera Flash Cable
The weight and overall dimensions of modern strobe equipment regularly strain ‘hot shoe’ mounting fixtures. Fundamentally, the longer the strobe and the heavier the strobe head, the more leverage for torque against the relatively small mounting hardware.
The photograph above illustrates the point of failure, where the off camera strobe cable broke at the screw in attachment when a 1 meter light stand fell. The weight of the strobe on the cable mount snapped the screw fixture from the plastic casing.
Fundamentally the torque was introduced by process failure, in not sandbagging the light stand – even though a falling strobe in the woods would rarely harm anyone.
I was perplexed in this case, as I regularly seem to ‘drop test’ Nikon flash equipment – nothing has ever broken. Once back to the studio, in examining the failed cable (which still functioned but could not be secured to a stand), it turned out to be a non-Nikon cable. It came bundled with a light modifier, and somehow found its way into the location kit – they look just like the manufacturer’s cable.
Postmortem: always sandbag light stands and before affixing equipment to them; use velcro straps with expensive flash units
Note: The OEM Nikon remote cables (Nikon P/N SC-29) have reinforced connection points, and a stronger plastic casing.