For single layer metallic grids, the simple theory Ulrich laid out works quite well. The functions | τ τ c a p ( ω ω ) | 2 and | τ τ i n d ( ω ω ) | 2 can be determined by measuring the transmission through the filter, and the phases ϕ ϕ c a p ( ω ω ) and ϕ ϕ i n d ( ω ω ) can be measured by setting two identical grids variable distances apart and measuring the interference maximum of Γ Γ ( ω ω ) ϕ ϕ ( ω ω ) as a function of separation. Measurements of very thin nearly ideal grids show the expected behavior and have very low absorptive loss.