I have about twelve Topcor lenses but not that one.
Can you just show the MTF curve?
Durlacher said:
Regrettably, I was unable to find any mtf charts for the 58 1.4 - despite extensive research and reading of period publications.
The reason for that is historical evolution...the MTF measurements simply were not commonly in use! As explained by Norm Koren in
http://www.normankoren.com/Tutorials/MTF.html
Introduction to modulation transfer function (MTF)
Back in my youth, lens and film resolving power was measured in lines (or line pairs) per millimeter (lp/mm)— easy to understand, but poorly standardized. It was obtained by photographing a chart (typically the
USAF 1951 lens test chart) and looking for the highest resolution pattern where detail was visible. Because perception and judgment were involved, measurements of the same film or lens were highly inconsistent. Lines per mm would have been more useful if it were measured at a well established contrast level, but that was not so easy; it would have required expensive instrumentation. The problem of specifying resolution and perceived sharpness was solved with the introduction of the
Modulation transfer function (MTF), a precise measurement made in
frequency domain. This made optical engineers happy, but confuses many photographers. The goal of this series is to shed light on the subject (literally as well as figuratively).
But even the publication of MTF curves are not done in a uniform manner by all parties, as explained in
https://www.japanistry.com/mtf-curves/
"As pointed out, Nikon perform their MTF test with the lens only wide-open; whereas Canon perform their tests wide-open and at ƒ/8.0. This is why the Canon MTF graph shown above had eight lines versus Nikon’s four. Testing at ƒ/8.0 provides useful information because (1) it provides a point of consistency when testing two lenses with the same focal length but different maximum apertures e.g. 50mm ƒ/1.2 vs 50mm ƒ/1.8, and (2) not all photographs are taken at maximum aperture—a landscape photographer for instance would value the data at ƒ/8.0 vs wide open."
And even the very definition of MTF curves changes over time! Canon RF lenses are measured differently from all its prior lenses. As explained by Canon in
https://www.usa.canon.com/learning/...ist/reading-and-understanding-lens-mtf-charts
"2018: CHANGES IN CANON'S MTF EVALUATION METHODS, AND MTF CHARTS
In late 2018, coinciding with the introduction of Canon’s RF lens series for full-frame EOS R-series mirrorless cameras, Canon optical engineers made across-the-board changes to the way they evaluate lens optical performance, and how it’s displayed in MTF charts.
Fortunately, for consistency, Canon has updated the MTF charts for all current EF, EF-S, TS-E, MP-E, and EF-M lenses, so that meaningful comparisons can still be made by critical Canon users. Canon RF lenses, of course, are also graded on these updated MTF evaluation methods.
- Previous Canon MTF evaluation standards were calculated from criteria derived years ago from the film (analog) era, and not changed until late 2018
- Optical performance is now measured using more critical, demanding standards, based on digital imaging and the use of high-resolution digital image sensors in digital SLRs and mirrorless cameras
- Canon MTF charts will now only display MTF results at the lens’ widest maximum aperture — previous Canon MTF charts displayed results at both maximum aperture, and at an effective f/8
Because the new, updated MTF measurement system used by Canon is based on stricter, digitally-oriented criteria, if you compare older and new MTF charts, any previously-introduced lens may seem as though some aspects of its MTF results are now lower than before. Rest assured this is because it’s now being graded using more demanding criteria, and does not represent an actual reduction in a given lens’ actual ability to deliver contrast or resolution than it previously did."
...so, by Canon's own declaration, you CANNOT compare older MTF curves against its own current MTF curves (much less directly compare those from different test centers)!