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Mitigating Longitudinal Chromatic Aberration by Stopping Down

Moderate control of secondary color errors requires 2 stops with most lenses, 3 stops for nearly complete control, 4 stops to go neutral.

For example, stopping down an f/2 lens to f/4 eliminates most of the secondary color errors, f/5.6 is nearly neutral, but f/8 is required for strongly defocused areas.

The Canon 50mm f/1.2L is a well corrected lens, as is the 85/1.2L II, but both are from from being free of color errors (not feasible with f/1.2 lenses). With both lenses, stopping down to f/2.8 (2+ stops) controls secondary color fairly well, but aperture f/5.6 is nicely neutral. More defocus would let the color areas linger for longer.

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  • Eases into photographic challenges with an introductory section.
  • Covers aspects of digital sensor technology that relate to getting the best image quality.
  • Technique section discusses every aspect of making a sharp image handheld or on a tripod.
  • Depth of field and how to bypass depth of field limitations via focus stacking.
  • Optical aberrations: what they are, what they look like, and what to do about them.
  • MTF, field curvature, focus shift: insight into the limitations of lab tests and why imaging performance is far more complex than it appears.
  • Optical aberrations: what they are, what they look like, and what to do about them.
  • How to test a lens for a “bad sample”.

Intrigued? See Focusing Zeiss DSLR Lenses For Peak Performance, PART ONE: The Challenges, or (one topic of many) field curvature.

   
f/1.2 — strongly magenta/green
f/2.8 — much more neutral
f/5.6 — neutral
Canon 50mm f/1.2L

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