Panasonic Lumix S 50 mm f/1.8
7. Coma, astigmatism and bokeh
Like in the case of longitudinal chromatic aberration the more complex optical construction of the Panasonic S 50 mm f/1.8 makes a step in the right direction, limiting the aberrations, described in this chapter. Still they aren't reduced completely. The dimensions of a diode increase as you move further away from the frame centre and in the very corner of full frame the diode turns into a small disc. This effect is visible but not very pronounced and allows us to assess the performance in this category in a positive way.
| Center, f/1.8 | Corner APS-C, f/1.8 | Corner FF, f/1.8 |
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| Center, f/2.5 | Corner APS-C, f/2.5 | Corner FF, f/2.5 |
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In order to present a comprehensive performance in this category we also decided to show crops of photos of the sky taken from the left-hand upper corner of full frame. This time, however, we show shots taken by f/1.8, f/2.5, and f/3.5. The test with using the stars is always a tad more demanding. In previous photos the diode changed into a disc but now you can notice slight wings that decrease on stopping down the aperture to f/2.5 and they disappear completely by f/3.5.
| Corner FF, f/1.8 | Corner FF, f/2.5 | Corner FF, f/3.5 |
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Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 10.6%. It is a result on the borderline between low and medium levels. It doesn't provide us any reasons to complain but certainly it influences the in a negative way the maximum results of the tested lens.
Out-of-focus images produced by the Panasonic S 50 mm f/1.8 are sensible but nothing more. First, you can notice here the influence of as many as three aspherical elements in the system that create an effect of onion-ring bokeh. Also you can notice a presence of a brighter rim which intensity increases on stopping down. Mechanical vignetting, though, is nothing you can complain about as it disappears completely on stopping down the aperture by 2 EV.
| Center, f/1.8 | Corner APS-C, f/1.8 | Corner FF, f/1.8 |
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| Center, f/2.5 | Corner APS-C, f/2.5 | Corner FF, f/2.5 |
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Center, f/3.5 | Corner APS-C, f/3.5 | Corner FF, f/3.5 |
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