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Spherical Aberration
Spherical aberration is the differential focus of light rays from different zones of the lens. Rays from the peripheral and intermediate zones of the lens focus at slightly different distances than those near the center, resulting in a smearing of focus. As such, it affects the image over the entire frame, including the center.
Spherical aberration produces a veiling halo around the tightest group of rays, so the subject presents as a sharp “core” image, but with low contrast due to a diffuse halo surrounding it (a defocused image of the sharp core)— this is the reason for the hazy (low contrast) image quality.
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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.
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