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S Dilworth wrote:
In any case, the Canon MTF charts have too much information to absorb at once, so we have to concentrate on one aspect or another of performance to take in anything at all.
Back to the corner numbers, then. Iíd expect two people to read the charts slightly differently, perhaps by a few per cent in some cases, but some of your numbers are very different from mine.
According to EF Lens Work, the curve in question for the above data (tangential (or meridional) MTF at f/8 and 30 lines/mm) is the dashed, blue, thin line. For that line, for the...Show more →
Yeah, the Canon charts have way too much information crammed into way too small a space. You need a magnifying glass and a lot of patience to tease out all the relevant info. This is especially true of the newer lenses where you have a lot of lines squeezed in at the very top of the graph. But having converted the graphs from Canon's postage stamp-sized raster images into a mathematical representation I can freely combine elements of several MTF charts into single image which makes comparison of lenses (or rather of their idealized MTFs) a snap.
Below are comparisons of the 24-70/2.8 I & II, the 24-70/4 IS, and the 24-105/4 IS at 24mm and 70mm (except not the 24-105 at 70mm of course) both wide open and at f/8. The wide open data has been separated from the f/8 to minimize clutter, but a fair degree of clutter is inevitable when so much data is being presented. The graphs have been enlarged to make it easier for tired eyes.
In every chart the 24-70/2.8 (version 1) is represented by black lines, the 24-70/2.8 II by blue lines, the 24-70/4 IS by red lines, and the 24-105/4 IS by green lines. As in the original Canon charts: thick lines represent contrast (10 cy/mm), thin lines represent micro-contrast/sharpness (30 cy/mm), solid lines are sagittal (radial), and dashed lines are meridonal (tangential).
All data adjusted for diffraction.