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EXCERPT page containing first few paragraphs. 2023-02-04 07:29:14

Your Lens Might Be Sharper Than It Seems!

Precise focus is critical to realizing the full resolution potential of today’s high-resolution digital cameras, yet the little-understood phenomenon of focus shift undermines that goal, whether focusing with autofocus or manually. Understanding focus shift will help you get the most out of some lenses that exhibit it.

Focus shift is not a lens defect, but it is a side effect of the optical design choices: uncorrected spherical aberration. Spherical aberration that is considered a desirable trait for certain “classic” lenses because it can lend a dreamy and soft look when a lens is shot wide open. The Zeiss 85mm f/1.4 Planar is one such lens where spherical aberration is “designed in” with the understanding that the applications might include portraiture. Many fast lenses exhibit uncorrected spherical aberration. The Nikon 105mm and 135mm “DC” lenses incorporate spherical aberration explicitly as a feature; the lenses include a ring to vary the amount for soft-focus effects.

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Diglloyd Making Sharp Images articulates years of best practices and how-to, painstakingly learned over a decade of camera and lens evaluation.

Save yourself those years of trial and error by jump-starting your photographic technical execution when making the image. The best lens or camera is handicapped if the photographer fails to master perfect shot discipline. High-resolution digital cameras are unforgiving of errors, at least if one wants the best possible results.

  • 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.

Focus precision matters with some subjects, and focus shift can wreak havoc.
Here the problem was avoided by focusing and shooting at f/1.4, and getting the focus precisely on the moving Mallard’s eye at left.
(Zeiss ZE 85/1.4 Planar)

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