![]() ![]() While this may not sound impressive, the quality of the blur in the focus transition zone is actually very good (smooth) for a standard zoom lens - both in the background and foreground.īokeh fringing is an axial color fringing effect. "Cat's eyes" in the image corners are not so much of an issue surprisingly although you can spot a slight deterioration at f/1.8. The circular shape remains mostly intact till about f/4 (tested at 35mm). ![]() Out-of-focus highlights show a near-circular shape at large aperture settings but the inner zone of these discs is clearly nervous. However, to be fair - this applies to most standard zoom lenses. The Sigma is pretty good but it has its issues here. While not a number game, the quality of the bokeh (out-of-focus blur) is a major aspect for an ultra-large aperture lens. They remain below 1px on the average at the image corners at 18mm and 24mm and are negligible at 35mm. Lateral chromatic aberrations (color shadows at harsh contrast transitions) are low and not disturbing. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. Please note that the MTF results are not directly comparable across the different systems!īelow is a simplified summary of the formal findings. The centering quality of the tested sample was good. At f/8 you may spot a slight downturn due to diffraction but this is still rather irrelevant here. However, the glory doesn't stop here - the borders are easily on a very good level at large apertures and even touch excellent levels at medium aperture settings. The center performance is already excellent at f/1.8 but downright outstanding between f/2.8 and f/5.6. The Sigma 18-35mm f/1.8 DC HSM | A produced nothing short of stunning resolution figures in the MTF lab. ![]() However, the issue is mostly resolved at f/2.8 and gone beyond. This also applies to the Sigma - the vignetting varies around the 1.5EV (f-stop) mark at f/1.8. Ultra-low aperture lenses tend to show heavy light falloff at max. ![]()
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