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EXCERPT page containing first few paragraphs. 2021-09-19 21:13:30

Localized Contrast Enhancement over Entire Image

The human visual system perceives sharpness and contrast together—more contrast means more perceived sharpness.

A final step in adding “snap” to an image (monochrome or otherwise) involves localized contrast enhancement, applied over the entire image.

“Localized” refers to math being done over a relatively small area (the Radius in pixels) as compared to a global effect as with a Curves layer. This differs from regular sharpening (as with Smart Sharpen), which might use a Radius of 0.7 pixels or so.

The trick here is a low level of sharpening (the Amount) applied over a fairly large areas (a 50.0 pixel Radius is about 7850 pixels). It is thus adaptive to the subject matter but in pretty broad strokes, so to speak.

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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.

Wide-radius Unsharp mask for localized contrast enhancement

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