Which type of filter is least likely to be used for light alteration in video production?

In video production, each type of filter serves a specific purpose in manipulating light to achieve desired visual effects or corrections. A flash filter is primarily designed to be used with flash photography to control the light output from a flash unit. Its main function is to soften the harshness of direct flash light or to balance the colors when a flash is fired, making it less relevant in the context of continuous lighting setups commonly used in video production.

On the other hand, ND filters (neutral density filters) are crucial for reducing the amount of light entering the lens without affecting the color balance. They are frequently used to manage exposure, allowing for wider apertures or slower shutter speeds in bright conditions. Gradated filters help create smooth transitions in exposure, such as balancing bright skies against darker landscapes. Polarizing filters are effective in reducing reflections and glare, enhancing color saturation, and increasing contrast, which can greatly benefit video visuals.

Given this context, while other filters are integral to light manipulation in video production, a flash filter is least likely to be employed as it mainly pertains to still photography and has limited application for altering light in video contexts.