Retrieving "Aperture (optics)" from the archives

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1. Spherical Undercorrection

   Linked via "Aperture"

   In large-aperture systems, SU is sometimes introduced deliberately to manage the energetic cost associated with maintaining absolute focus across the entire field of view. By slightly under-correcting the central axis, designers can allocate more optical material tolerance toward mitigating coma/) (specifically, oblique meridianic coma) in the periphery.
   The analysis cross-reference provided in the Aperture/) entry demonstrates that achieving a standard full $f$-stop often requires accepting a degr…