This region of space was selected in part because it is located behind several galaxy clusters that create a natural magnification effect called gravitational lensing.

Barreldistortion

Wide-angle lenses in retrofocus design (back focal lengths greater than focal length) tend to generate barrel distortion, telephoto lenses (overall length below focal length) tend to generate pincushion distortion.

The region of the highest cone density lies within the foveae, allowing the birds to clearly perceive distant objects through magnification.

Pincushion distortionradiology

Image

The percentage of the maximum distortion is measured from the centre to the image corners, as this is where the maximum distortion appears. In clearly simplified terms, the increase of the error can be described as linearly increasing from the centre of the image to the image margin.

Pincushion distortionlens

Josh Bouganim, a software engineer, proposed examining both cards under 200x magnification to see if the threads in the swatches matched.

Pincushion distortionphotography

A non-symmetric design of the lens and an aperture before or behind the optic centre of the lens lead to image distortions. The image can be curved in a barrel-shaped or cushion-shaped way.

Distortion is a rotationally symmetric image error which increases from the centre of the image towards the image margin. In the course of this there is a local modification of the image scale within the image plane, which can be very disturbing for measuring applications. If the magnification rises towards the margins of the image field, a square is distorted in a cushion-shaped way. In the reverse case we speak of barrel-shaped distortion.

In almost all applications, distortion is disturbing. The extreme fisheye perspective of a very short focal length, however, can help in case of very close distances to look at the sides of a cavity. Typical examples of this are inspections of bores, needle roller bearings, thread pitches, etc.

By comparing the apparent positions of the holes as viewed by the optical microscope with the actual positions, the researchers assessed errors from magnification calibration and image distortion of the optical microscope.