A light-control grid uses cells to restrict light travelling at wider angles from a fixture or modifier. Fabric eggcrates are common on softboxes and frames; rigid honeycomb grids are common on reflectors and panels. Here, grid refers to the optical accessory, not an overhead rigging structure.
What a grid changes
A grid controls spread by obstructing some light paths. It does not increase output by focusing light in the way an optical attachment can. Its effect on illuminance, beam transition and apparent source area depends on the grid, the light behind it and the viewing position.
Practical example
A softbox beside an interview subject may also brighten the wall behind them. Fit its compatible grid, re-aim if needed and compare the subject and wall again. Check every actor mark: a person moving across the controlled field can lose light more quickly than expected.
Read the complete setup
Treat a stated angle as a manufacturer’s description of that grid and test arrangement. Do not assume that two products marked 40° have identical distributions or a sharp cutoff at 40°. Confirm the dimensions, attachment method and whether the grid is intended to sit over the diffusion. Re-measure exposure after fitting it, and keep fabric clear of anything the manufacturer identifies as a hot surface.
Related terms
Spill · Diffusion · Soft Light · Beam Angle · Flag
References
Aputure: Light Box 60×90 and fabric grid · ARRI: honeycomb and eggcrate accessories