The numbers below represent MTF-50 at aperture f/4. The NEX-7 was set at ISO 400 and each lens was manually focused and bracketed so that focus errors were eliminated.
from Imatest.
Device or system sharpness is measured as a Spatial Frequency Response (SFR), also called Modulation Transfer Function (MTF). MTF is the contrast at a given spatial frequency (measured in cycles or line pairs per distance) relative to low frequencies. The 50% MTF frequency correlates well with perceived sharpness— much better than the old vanishing resolution measurement, which indicated where the detail wasn’t.
Now let's look at the test results at aperture f/4.
Lens Max Avg Sony 16mm f/4 915 646 Sigma 19mm f/4 920 765 Sony 24mm f/4 1000 795 Sony 18-200 f/4 855 680 Sony 18-55 @20 f/4 855 640 Sony 30mm f/4 940 725 Sigma 30mm f/4 1040 840 Sony 50mm f/4 885 835 Leica 50mm f/4 1020 870
Photo by jerome_Munich
What can we learn from this test? At f/4 most of these lenses, from $4000+ Leicas to $200 Sigmas, will be separated by the technique of the photographer with regards to resolution. Keep the camera still when taking a shot by using a high shutter speed, a tripod, a remote shutter release, etc. If you want maximum resolution, it looks like the Sigma 30mm DN Lens is the best bang for the buck.
Here's a quick quote from the article regarding the NEX-7 vs the Canon 5d Mark III and the Nikon D800.
- (NEX-7) resolution at f/4 with a good lens is about what we see with a Canon 5DII or III (1050 / 800 or so LP/IH) with a good lens, not quite as good as a Nikon D800 (1200 / 1000 LP / IH).
Read the complete NEX-7 Lens Resolution Comparison by RC at LensRentals.com.
Read more about sharpness from Imatest.
Thanks RC!
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