Q: What are the differences between Achromatic, Semi-Plan, and Plan objectives?
A: Achromatic objectives feature a single achromatic lens, correcting color aberrations and providing a flat field in the central 65% of the image. Semi-Plan objectives offer an 80% flat field, bridging the gap between achromatic and plan objectives. Plan objectives provide superior correction for color and spherical aberrations, offering a flat field in approximately 95% of the image.
Original Page: What are the differences between Achromatic, Semi-Plan, and Plan objectives?