TS Ploessl 20mm
Very good sharpness within 30° field of view. Towards the edge not convincing.
x-axis: distance from optical axis in °, y-axis: resolution in arc minutes
Apparent Field of View:
The apparent field of view is approx. 45°
Very good contrast because of good multicoating and use of just four lenses.
Very slight cushion distortion.
Simple, but not bad. Unfortunately no blackened filter thread.
Very good and inexpensive Ploessl. Just a small minus for insufficient edge sharpness.