4 aspherical (of which 2 advanced), 3 extra low dispersion
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With activated image auto-correction it's probably the best APS-C standard zoom lens there is on the market today. It shows no weakness in terms of image resolution and there are no CAs to speak of. The corrected distortions are - obviously - nothing to worry about [...] The build quality is very high [...] The biggest drawback is probably the lack of an image stabilizer.