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Unmodified Nikon D700 (left), D700 with AA filter removed (right)
Mouse over “hot rod” version

Blur from Anti Aliasing Filters

Most digital cameras have an anti-aliasing filter installed over the sensor, also known as an optical low-pass, or blur filter. This filter is generally integral to the sensor cover glass over the sensor itself.

Moiré

The purpose of the anti-aliasing filter is to reduce detail aliasing, moiré, and color aliasing, an effect that occurs when detail approaches the sensor resolution, the goal being to avoid moiré and similar effects. The filter is not needed for true-color cameras such as the Sigma DP Merrill line or monochrome cameras such as the Leica M Monochrom.

As of 2014, more and more cameras are going without such sharpness-robbing filters: Nikon D800E, Nikon D3200, Ricoh GR, Sony A7R. The Pentax K3 even has a sensor that vibrates selectively, so that the AA filter can be present or absent by setting. The reason for abandoning the anti-aliasing filter more and more is the increasing resolution of digital sensors; at some point the lens becomes a limiting factor, effectively its own blur acting as an AA filter (as does diffraction).

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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.

Color aliasing — moiré (Leica S2)

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