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Covington Innovations Home > Astronomy and Astrophotography > Links > Digital SLR Notes > Lens Test Links
Lens Test Links
Compilations of lens tests
AF SLR Lens Test Guide (Photozone web magazine)Lens tests on Photodo.com including measured MTF curves
There are many others. Search Google for lens test and/or the particular lens you are interested in.
MTF curves
MTF stands for modulation transfer function. An MTF curve indicates the level of contrast with which a lens can reproduce a relatively fine target (10 or 30 lines/mm) across the field.This is much more informative than simply saying "This lens resolves 100 lines/mm" (etc.) because resolution depends on contrast; boosting the contrast during the test will raise the lines/mm. Also, if a lens produces a sharp image superimposed on a blurred one, it will have high resolution but poor MTF.
How to read an MTF curve (Canon)
(What you want is a lens whose sagittal and meridional curves, in each pair, stick fairly close together, and whose 30 lines/mm curve stays above 0.6 almost all the way to the edge. Lower standards are appropriate for wide-angle lenses and wide-range zooms. Remember that with a DSLR, you actually only need to go out to about 15 mm from center, not all the way to the edge.)Canon MTF curves are published in the book EOS Lens Work III and in the online Japanese lens catalog here. Scroll down to the bottom of each lens's web page to see the MTF curves. Each chart has 2 pairs of curves, black (for the lens wide open) and blue (for the lens at f/8).
Nikon MTF curves are published on Nikon Japan's global web site and are in much the same format as Canon's. In English, they are available here:
You can also find them at the bottom of the Japanese data page for each lens, which you can find through these links: They contain only data for the lens wide open (like the black curves in Canon's charts).
[Thanks to Gisle Hannemyr for these links!]Hint: If you cannot read Japanese, you can still navigate Nikon's Japanese web site by looking at the links displayed in your browser; the file names and folder names are in English. Also, a moderately good Japanese-English translator is available here.
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