A measure of the ability of a lens or optical system to form separate and distinct images of two objects with small angular separation. Note 1: An optical system cannot form a perfect image of a point (i.e., point source. ) Instead, it performs what is essentially a Fourier transform, and the resolving power of an optical system may be expressed in terms of an optical transform (transfer function) called the modulation transfer function (MTF. ) Note 2: The resolving power of an optical system is ultimately limited by (a) the wavelength involved, and (b) diffraction by the aperture, a larger aperture having greater resolving power than a smaller one. Note 3: While the term "resolving power" is usually applied to the traditional optical regime, it may also be applied to, e. G. , the radio regime, especially at, but not necessarily limited to, very short wavelengths, on the order of millimeters or centimeters. Note 4: Especially at longer wavelengths, certain schemes may be employed to create a very large synthetic aperture, thereby increasing resolving power. Some of these schemes involve precise measurements of the respective times of arrival, at geographically separate locations, of signals from separate sources. Synonym resolution.