What is the difference between achromatic, semi-planachromatic, and planachromatic objectives?
Each type of objective is color corrected to a higher degree than the previous one. In everyday terms, achromatic objectives afford approximately 80% of the field of view in focus from the center out to the edges. Semi-planachromatic afford approximately 90% and planachromatic afford approximately 100%. The better the color correction, the more cost.
