Equations for the optical transfer functions (OTFs) are derived for imaging systems operating in the atmosphere that consider the finite outer scale of turbulence for short and long times of exposure. The effect of the outer turbulence scale has been analyzed on the form of these OTFs. The integral resolution of the optical system has been calculated for different values of the outer scale of turbulence. It is shown that the finite scale of turbulence, even though it is larger by an order of magnitude than Fried’s radius, should be considered to estimate the system resolution.