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60MP Sony A7R IV

Case Study: Major Sharpness Gains via Ideal Focus with Lenses having Peripheral Forward Field Curvature (Pine Creek High Peaks)

There is little tolerance for focus errors on high resolution cameras (focusing along with field curvature and focus shift). The Sony A7R IV used here has 3.8 micron pixels, as does the Fujifilm GFX100 and the PhaseOne IQ4, all state of the art as of late 2019.

Peripheral forward field curvature means that the zone of sharpest focus is bowl-shaped, with the edges focusing closer than the center. The “bowl” can be relatively flat throughout, or it can have steeply-rising sides (edges of the frame or corners), or any variant in between.

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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.

f4 @ 1/640 sec electronic shutter, ISO 100; 2019-10-19 12:10:27
Sony A7R IV + Sigma 35mm f/1.2 DG DN Art + polarizer Breakthrough Photography X4
ENV: Pine Creek, altitude 8900 ft / 2713 m, 50°F / 10°C
RAW: LACA corrected, vignetting corrected
focus at center

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