An apparatus (2) and method, for measuring process-induced features in a transparent sheet (10). The apparatus includes a light source (100), an imaging device (80), and a support structure (30) disposed between the light source and the imaging device. The support structure is configured and arranged to support the transparent sheet so that measurement error induced by the support structure is viewed by the imaging device as extending along or parallel to a first axis (46, 54) that is oblique to a second axis (22, 24) along or parallel to which the process-induced features in the transparent sheet extend when viewed by the imaging device.