Canon RF 35mm f/1.8 Macro IS STM vs Sigma 18-50mm f/2.8 DC DN Contemporary (Canon RF)

The Sigma 18-50mm f/2.8 DC DN Contemporary (Canon RF) is a zoom (18-50mm) and the Canon RF 35mm f/1.8 Macro IS STM is a 35mm prime. The zoom gives you framing flexibility from one lens; the prime trades that for a fixed focal length that's usually brighter (f/1.8 vs f/2.8) and lighter to carry. Choose flexibility or a fast single focal length.

Choose the Canon RF 35mm f/1.8 Macro IS STM if you want more light and background blur — f/1.8 is faster than f/2.8, better for low light and subject separation. Choose it if you prefer a fast, compact single focal length — a 35mm prime over a zoom. Choose it if you shoot handheld or on an unstabilised body — it has optical stabilisation, the other doesn't.

Choose the Sigma 18-50mm f/2.8 DC DN Contemporary (Canon RF) if you need more reach — it goes to 50mm vs 35mm for distant subjects, wildlife and sport. Choose it if you shoot wide — it starts at 18mm vs 35mm for landscapes, interiors and architecture. Choose it if you want one-lens flexibility — a 18-50mm zoom covers what the fixed 35mm can't reframe. Choose it if you work outdoors — it's weather-sealed against dust and moisture; the other isn't.

Aperture: the Canon RF 35mm f/1.8 Macro IS STM opens to f/1.8 vs the Sigma 18-50mm f/2.8 DC DN Contemporary (Canon RF)'s f/2.8 — more light and shallower depth-of-field.