Since DxOMark measurements are performed on RAW images, an
imaging sensor is required to perform measurements. While this
statement is obvious, when talking about optical measurements,
it is very common to refer to lens performance alone. However,
sensors significantly influence optical performance, so it makes
a lot of sense to evaluate and compare lens-camera combinations,
rather than just lenses alone. Lenses can often be used on
different sizes of sensors—for instance, most APS-C or APS-H
cameras can mount lenses originally designed for 24x36mm
cameras. In this case, the generated picture is a “crop” of the
picture that a camera with a larger sensor would generate.
Obviously, if optical performance decreases from center to
corners on a 24x36mm camera, the optical performance on a
smaller sensor should be better, and this is true for
distortion, chromatic aberration, vignetting and resolution. In
the case of resolution, since results are normalized (stretched
in this instance) to a 24x36mm output, the reso