Is the canon rf 135mm f 1 8l is usm sharp wide open?

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From Canon RF 135mm f/1.8L IS USM: Canon RF 135mm f/1.8L IS USM: A prime lens by Canon for Full frame cameras, 135mm f/1.8. Specs - Maker: Canon - Focal length: 135mm (prime) - Maximum aperture: f/1.8 - Made for: Full frame sensors - Mounts: Canon RF - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Canon RF): as marked, 135mm. - On APS-C (Canon) (Canon RF): like 216mm on full frame; f/1.8 gives about the depth of ...

From Lenses: Aperture: The f-number says how wide the lens opens. Smaller numbers let in more light: f/1.8 lets in about ten times as much light as f/5.6, more than three stops. A wide aperture means faster shutter speeds in dim light and more background blur. Zooms with a constant aperture, like a 24-70mm f/2.8, keep the same exposure throughout the zoom range; cheaper zooms get darker as you zoom in.

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