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Lens review

Yongnuo YN 50 mm f/1.8

26 January 2015
Szymon Starczewski

4. Image resolution

The resolution test (meaning MTF50 function values) of the Yongnuo 50 mm f/1.8 lens was based on RAW files from the Canon EOS 5D Mk III. In the case of that reflex camera the decency level is situated aroung 30-32 lpmm and the best fixed-focal lenses can get as high as 44-47 lpmm.

Let’s check how the tested instrument compares here. Its performance in the frame centre, on the edge of the APS-C sensor and on the edge of full frame, depending on different aperture values, is presented in a picture below.

Yongnuo YN 50 mm f/1.8 - Image resolution

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At first glance you can tell the Yongnuo performs noticeably worse than the Canon 1.8/50 II. Especially its performance by f/1.8 and f/2.0 is disappointing because the MTFs are distinctly below the decency level. In order to enjoy an acceptable image quality in the frame centre you have to stop down the tested lens to near f/2.5. In the case of the edge of the APS-C sensor you get sensible MTFs after stopping down the aperture to almost f/4.0 and on the edge of full frame you have to employ f/5.6. Such a performance can only be called weak; still in order to defend the Yongnuo a bit you should mention the fact that even such a lens as the Nikkor AF-S 50 mm f/1.8G had similar problems on the edges of both types of sensors.

Here the maximum results in fact remain our only consolation. The tested lens was able to reach 44 lpmm by f/5.6 and it is a value it shouldn’t be ashamed of, unobtainable by many zoom lenses, even those good ones, and a part of older “primes”. Of course you can also say that you don’t buy a fast lens in order to close it down to f/5.6 very often.

At the end of this chapter traditionally we present crops of our resolution testing chart, taken from JPEG files which were saved along RAW files used for the analysis above.

Canon 5D MkIII, JPEG, f/1.8
Yongnuo YN 50 mm f/1.8 - Image resolution
Canon 5D MkIII, JPEG, f/4.0
Yongnuo YN 50 mm f/1.8 - Image resolution