2 asferici, 5 a dispersione super bassa, 2 a dispersione tipo fluorite
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Dustin Abbott It is an excellent lens in many ways, but probably not one that will make it into my bag. It is too large to be just a “bring along” lens [...]. The build quality feels excellent (...) , but the lack of any weather sealing is a serious shortcoming in a lens like this [...]. If you need great low light performance in a wide angle lens for events or wedding work, it is hard to think of a better alternative. The resolution from the lens is fantastic.
Obiettivo Sigma 20mm f/1.4 DG HSM Art (per Canon EF)