LensTip.com

Lens review

Canon EF 50 mm f/1.8 STM

11 July 2015
Szymon Starczewski

8. Vignetting

Let’s check how the Canon 1.8/50 STM manages vignetting on the smaller Canon 50D sensor first; the appropriate thumbnails are shown below.

Canon 50D, f/1.8 Canon 50D, f/2.0
Canon EF 50 mm f/1.8 STM - Vignetting Canon EF 50 mm f/1.8 STM - Vignetting


At the maximum relative aperture the vignetting is moderate, reaching 22% (−0.72 EV). That aberration decreases to 17% (−0.55 EV) on stopping down the aperture to f/2.0 and disappears almost completely (6% and −0.19 EV) after employing f/2.8.

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Now it’s time to see how the situation changes when you progress to full frame.

Canon 5D III, f/1.8 Canon 5D III, f/2.0
Canon EF 50 mm f/1.8 STM - Vignetting Canon EF 50 mm f/1.8 STM - Vignetting
Canon 5D III, f/2.8 Canon 5D III, f/4.0
Canon EF 50 mm f/1.8 STM - Vignetting Canon EF 50 mm f/1.8 STM - Vignetting


The problems become serious here. At the maximum relative aperture the light fall-off in the frame corners reaches as high as 61% (−2.75 EV). On stopping down the aperture to f/2.0 you are able to decrease it to 56% (−2.34 EV). Also by f/2.8 you won’t have any problems with noticing that aberration because it amounts to 32% (−1.09 EV). Bad performance ends by f/4.0 where the vignetting decreases to 15% (−0.48 EV). By f/5.6 that aberration becomes practically imperceptible (10% and −0.32 EV).

As you see a slight decrease of the size of the casing and the diameter of the filter plus an addition in a form of the STM motor didn’t make the vignetting level increase significantly. The results of the tested lens are by about 1% higher than those of its predecessor but, taking into account the measurement errors of 2-3% you can’t really talk about noticeable differences here. Still the performance of both Canons in this category can hardly be called good. It’s worth reminding here that both Nikkors, the AF 1.8/50D and the AF-S 1.8/50G, at the maximum relative aperture had the vignetting near 41-44% - they fared much better.

Canon EF 50 mm f/1.8 STM - Vignetting