A snoot is a cylindrical or sometimes conical reflector that fits on the front of a fixture to focus the light output into a narrower beam. This is useful not only for creating a focused beam of light on a subject, but it’s also a great way to control spill.
For instance, when used in a portrait setup, snoots can be used as a hair light and a background light. On the background, the snoot will create a circle of light that’s narrower or wider based on the distance from the light to the background. Snooted light can be a fairly hard-edged transition from light to shadow, especially when compared to a grid. The smaller the diameter of the snoot, the narrower the beam of light will be; the longer the snoot, the more defined the edge will be.
As a hair light, an open dish reflector would theoretically do a fine job, but it would scatter light everywhere, from the background to the lens. Not only does that spilled light change the look of a scene, but it could ruin it with flare. By using a snoot, the light is focused on the subject and spills neither on the background nor the lens.
Optical snoots are similar to the basic reflector and tube design, but they feature internal moving lenses that focus the beam of light. Optical snoots have a devoted following among photographers who need precisely sized and shaped light.
A grid spot (often known as a grid or honeycomb for the honeycomb-like hexagonal shapes into which the metal is divided) is another great way to focus light into a tight beam. If the grid is circular in shape, and fits into a seven-inch silver dish reflector on a studio strobe (a very common application), the light will be focused into a circular shape. If the grid is rectangular and placed on a rectangular hot-shoe strobe (another common use), the focused beam will maintain that shape.
Whatever the shape of the grid, light can only pass through in one direction, dictated by how big or small the individual cells of the grid are. The smaller the cells, the tighter the focus—much like with the opening on a snoot. Grids are usually measured in degrees—from 10º to 50º, commonly, with 10º producing the tightest circle of light.