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EXCERPT page containing first few paragraphs. 2023-02-04 07:14:05

Effects of Diffraction Blur on Color Aliasing

Cameras without an anti-aliasing filter are prone to high-frequency artifacts which show up as colored speckles or edges aka color aliasing. These “Christmas tree” effects can be very distracting in an image that is reproduced at a larger size.

By stopping down, diffraction begins to reduce aliasing artifacts by introducing a level of blur by degrading contrast at all structure sizes, and by making a larger blur circle, effectively acts like an anti-aliasing filter. The aperture at which this occurs depends on the size of the photosites, and in rough practical terms, the sensor size*.

* Strictly speaking the sensor size has nothing to do with it, but there is a coupling: larger sensors generally have larger photosites. Moreover, depth of field requires more stopping down for equivalent depth of field on larger formats.

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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.

f11 @ 1/125 sec, ISO 80; 2010-10-19 14:46:14
Leica S2 + Apo-Macro-Summarit-S 120 @ 120mm

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