Sigma's constant f/2.8 DX telephoto for Canon — the 50-150mm APO II for APS-C sports.
The Sigma 50-150mm f/2.8 EX DC HSM APO II is a constant-aperture telephoto zoom designed exclusively for APS-C Canon DSLR cameras, providing a 75–225mm full-frame equivalent range. The 'II' suffix marks the second major revision with updated optical construction. It carries the APO designation, indicating low-dispersion glass for chromatic aberration control.
The lens delivers a constant f/2.8 aperture across its 50–150mm range, uses HSM autofocus for fast and quiet operation, carries the DC designation confirming its APS-C-only image circle, and includes APO glass elements to suppress colour fringing. The EX designation indicates Sigma's professional-tier build quality for its era.
The 50–150mm f/2.8 focal range on APS-C bodies is equivalent to a 75–225mm fast telephoto zoom on full-frame — a range beloved by portrait and event photographers for its ability to isolate subjects while maintaining working distance. It is notably lighter than full-frame 70–200mm f/2.8 lenses while delivering similar practical performance on APS-C bodies.
Test HSM autofocus speed and tracking performance, particularly in lower light where the f/2.8 constant aperture is most useful. Inspect APO element coatings for any separation. Examine the zoom ring for smooth travel and verify there is no barrel creep when the lens is pointed downward.