Sigma's designation for lenses with a Helical Focusing system. These prevent the front element of a lens from rotating, making them ideal for filter use.
On sale: 29th Aug
Highlights this month include your essential guide to using prime lenses, plus 36 tips for better landscape images in our brand new 12-page Technique series, and we help you take control of your ISO settings. Plus much more!
Which of the new cameras announced so far this year are you most excited about?
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