EXCERPT page containing first few paragraphs. 2020-07-03 15:33:25
UA_SEARCH_BOT_null @ 3.214.184.223

Fantasy Land MTF

Many manufactures publish what are properly termed “fantasy” MTF charts.

Here are some of the sneaky approaches used (and generally not documented):

Computing (not measuring) MTF. Real lenses never are quite as good as the design and often not symmetric across the field.
Computed MTF is another fantasy in itself: there are the tolerances of surface shapes, glass parameter variations (which batch?), and lens element placement all of which mean that MTF measured in a real lens never lives up to its computed theoretical performance.
Calculation of ray aberrations might be done monochromatically or with very narrow bandwidth: every lens looks considerably better if (for example) only a narrow range of green light is used.
Calculation often ignores diffraction, which truly makes the MTF chart pure fantasy defying the laws of physics, even assuming a perfectly assembled lens, because in a real lens diffraction is unavoidable.
While a claim might be made of “white light”, computations might be made in ways that effectively make it a monochromatic figure.

Diglloyd Making Sharp Images is by yearly subscription. Subscribe now for about 13 cents a day ($50/year).
BEST DEAL: get full access to ALL 8 PUBLICATIONS for only 68 cents a day ($249.95)!

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.

Fantasy MTF chart that ignores diffraction
(computed, possibly with narrow bandwidth light)