16 In a cube $A B C D-A_{1} B_{1} C_{1} D_{1}$ with edge length 1, $E$ and $F$ are points on $A A_{1}$ and $C C_{1}$ respectively, and $A E=C_{1} F$. The minimum value of the area of quadrilateral $E B F D_{1}$ is $\qquad$.
(16) $\frac{\sqrt{6}}{2}$ Hint: When $E$ and $F$ are the midpoints of $A A_{1}$ and $C C_{1}$ respectively, the area of quadrilateral $E B F D_{1}$ can achieve the minimum value $\frac{\sqrt{6}}{2}$.