Distortion and chromatic aberration test chart
Generally, the function of rotationally symmetric optical systems is to form an image that is geometrically similar to the object except for in some particular systems, such as fish-eye lenses and eyepieces, where this condition is deliberately not maintained. Ideally, this function is accomplished according to the geometry of perspective projection. Departures from the ideal image geometry are called distortions.*
The TE251 test pattern is designed for the image quality measurement of distortion and chromatic aberration in digital imaging, e.g., with DSLR, compact camera or a mobile phone. It is based on the ISO 17850 Photography — Digital cameras — Geometric distortion (GD) measurements standard, which was released in 2015, as well as on other standards such as IEC 62676-5 and IEEE P1858 CPIQ.
The chart contains black crosses on a white background and is available as a reflective and transparent test target.
The image quality analysis of this special grid delivers the LGD (local or line geometric distortion), the TV distortion, the CA (chromatic aberration) and the LCA (longitudinal chromatic aberration).
A full distortion analysis can be done using the iQ-Analyzer software. The software will provide an assessment of TV distortion, LDG, LCA and CA.
*Read technote for more information on What is “lens geometric distortion”.