Canon EF 50mm f/1.8 STM – Test results
Resolution
Studying our lab results and sample images meticulously revealed signs of softness in the centre at f/1.8. However, stop down to f/2.8 and you’ll quickly notice that the centre immediately starts to sharpen up. The edges of images are perceptibly soft from f/1.8-f/2.8, but by the time you stop the lens down to f/4 and f/5.6 corner sharpness improves. Users who want to find the sweet spot and achieve ultimate sharpness should use the lens between f/8 and f/11. Close the aperture to f/16 and f/22 and diffraction has the affect of softening images.
Shading
Shooting wide-open at the maximum aperture (f/1.8) results in strong vignetting at the corners and it’s a similar story at f/2 where you can’t fail to notice the dark corners at the edges of the frame. Stopping the lens down to f/2.8 sees the effect of vignetting reduce significantly, and although still present it’s not as obvious in real-world images. Setting the lens to f/4 and beyond sees the traces of vignetting vanish.
Curvilinear distortion
As to be expected from a fixed-focal-length standard lens, distortion is well handled. Our distortion chart did show a little barrelling towards the corners, but it’s by no means anything to be concerned about and you’ll struggle to observe it in real-world use.
