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Sigma 18-35mm f/1.8 DC HSM
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The world fastest zoom lens (for APS-C sensors) with a fixed aperture, the Sigma 18-35mm f/1.8 DC HSM got reviewed. The lens, part of Sigma’s “Art” line-up, caused some hype when it was announced. Sigma called it UFO (Unbelievable F-stop Object). Some hands-on here and here.
Focus Numerique (google translated) tested a pre-production model, and writes:
The results of the new Sigma zoom are impressive and worthy of a professional optical 24×36 mm that opens to f / 2.8 constant! Of course, the best results are obtained with medium apertures between f / 5,6 and f / 8, though the sharpness is present in larger openings also. However there was a decrease of sharpness between the center and edges of images with larger apertures and f / 1,8 particularly.
Digifoto (no translation from Flemish) writes:
We were surprised again after seeing the test photos. You expect from a zoom lens at fully open aperture somewhat lesser performance in the corners. The Sigma 18-35mm f/1.8 however scored exceptionally well, even at the 18mm f/1.8 corner tightened remains very good. The bokeh of the lens looks very stylish, and distortion remains well within bounds.
Image samples of the Sigma 18-35mm can be seen at Dpreview.