\[\left( - \frac{1}{2} \right)^{16}\ :\left( - \frac{1}{2} \right)^{8} = \left( - \frac{1}{2} \right)^{16 - 8} =\]
\[= \left( - \frac{1}{2} \right)^{8} = {0,5}^{8}.\]