Tamron 90 mm f/2.8 Di III Macro VXD
7. Coma, astigmatism and bokeh
Center, f/2.8 | Corner APS-C, f/2.8 | Corner FF, f/2.8 |
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Center, f/4.0 | Corner APS-C, f/4.0 | Corner FF, f/4.0 |
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In order to present a full spectrum of results in this category we decided to show also crops taken from photos of starry sky taken from the upper left-hand corner of full frame. This time we focused on shots taken by f/2.8, f/4.0, and f/5.6. They show clearly that even on stopping down the aperture by 2 EV coma is not corrected completely and its effects can still be visible as a very small 'comma'. Of course it has to influence the tested Tamron's resolution on the edge of the frame and can be another reason why the values you see in the frame centre are so much higher than the results on edges of the frame.
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Corner FF, f/2.8 | Corner FF, f/4.0 | Corner FF, f/5.6 |
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Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 9.8%. It is a result on the borderline between low and medium level so not providing any serious reasons to complain. Of course it should be noted that the Sony and the Sigma presented here values of 3-5% so a bit lower.
The appearance of out-of-focus images produced by the new Tamron 2.8/90 is nice. There are no aspherical elements in the optical construction so it is difficult to expect any traces of onion ring bokeh; as a result the interiors of the circles are very smooth, with even light spread, and the rim, appearing on stopping down, is not especially intense. Still mechanical vignetting makes itself felt, even after stopping down the aperture by 2 EV. Once again it is an aftereffect of the long, narrow mechanical construction of the lens, closed from one side by a small front element.
Center, f/3.3 | Corner APS-C, f/3.3 | Corner FF, f/3.3 |
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Center, f/4.0 | Corner APS-C, f/4.0 | Corner FF, f/4.0 |
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Center, f/5.6 | Corner APS-C, f/5.6 | Corner FF, f/5.6 |
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