The MTF for a lens tells you how it affects contrast and resolution. You can quantify the performance of an imaging system based on its ability to provide images of a certain quality. Adequate image quality in one application may be insufficient in another. The key components of image quality are resolution, contrast, distortion, and perspective errors. I will describe a measurement that combines resolution and contrast in one standard specification.
Resolution is a measure of an imaging system's ability to reproduce object detail.
A low-resolution image contains blurry scenes in which objects lack detail. A high-resolution image provides crisp edges and includes much detail. Contrast also factors into image quality because it expresses how well an image differentiates between an object's shades of gray. Resolution and contrast are closely related. At increasing frequencies, optical information passing through a lens loses contrast.