planapochromat

A planapochromat is a type of photographic lens that corrects for chromatic and spherical aberrations. The "plana" prefix indicates that the lens is flat-field, meaning it produces sharp images across the entire frame, even at the edges. This is crucial for applications like aerial photography and microscopy where edge-to-edge sharpness is essential. The "apo" prefix signifies that the lens is apochromatic, meaning it corrects for chromatic aberration in three primary colors (red, green, and blue) rather than the two colors typically corrected in achromatic lenses. This results in significantly reduced color fringing, especially in areas of high contrast. Finally, the "chromat" part refers to the correction of chromatic aberration.

Planapochromat lenses are constructed with multiple lens elements made from different types of glass, including special low-dispersion glass. These elements are precisely shaped and arranged to minimize distortions and aberrations. The design of a planapochromat is complex, often involving ten or more individual lens elements. This intricate design contributes to their high performance and image quality. Due to their sophisticated construction and superior optical correction, planapochromat lenses are generally more expensive than standard lenses. They are commonly found in high-end photographic equipment, scientific instruments, and specialized imaging systems where the highest level of image fidelity is required.