What is the difference between achromat & plan achromat objectives?
Objectives are corrected for field curvature and color aberration. The difference between Achromats and Plan Achromats is the degree of the flatness of field. When the image is in focus from the center towards its edges; the field is said to be “flat”. In general, the flatter the field of an objective, the more lenses it contains and the more expensive the cost.
