EXCERPT page containing first few paragraphs. 2023-03-29 18:22:13
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Choosing a Test Scene for Evaluating Sharpness
A good comparison test uses a subject that reveals errors, focusing errors in particular since even a very small focus error invalidates a comparison.
Rules of thumb—
- Focus on a high contrast unambiguous target ;
- Include sufficient detail at a consistent distance across the frame in order to make evaluation of the results straightforward;
- Choose a subject with left-to-right uniformity (similar subject matter at the same distance), so that symmetry can be checked.
- Include detail in all areas of the frame so that asymmetric blur can be detected e.g., upper left corner vs upper right corner, etc. Blue sky is not helpful.
- Include foreground and background to detect focus error and consistency.
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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.
