Square filters are a filter system in which square or rectangular filters slide into a holder mounted in front of the lens. This category covers neutral density (ND) and graduated (GND) filters, polarizing and effect filters, filter kits, filter holders, adapter rings for holders and square filter cases from brands such as Cokin, NiSi, Fotocom, H&Y and Rollei.

Landscape photographers value this system because a graduated filter can be shifted to match the horizon, and one holder with adapter rings works on several lenses. When choosing, consider the system size, such as Cokin M, L or 100 mm, and your lens thread diameter.