Canon EF 50mm f1.8 II Review

Firstly, The Canon EF 50mm f1.8 II is a prime lens with a standard focal length of 50mm and a bright focal ratio of f1.8. Announced in 1991, it replaces an earlier 50mm f1.8 model, employing the same optics but housing them in a simpler all-plastic case to keep costs down; indeed it's the cheapest lens in the Canon EF catalogue, which in part has made it Canon's best-selling model.

The 50mm focal length delivers standard coverage on a full-frame body, or 80mm equivalent on a Canon APS-C body, which acts like a short telephoto. The f1.8 focal ratio can deliver a very shallow depth-of-field, allowing you to place a sharp subject against a blurred background, an effect desired by many portrait photographers. The f1.8 focal ratio also means the lens can gather four times more light than a lens at f3.5 or just over eight times more than one at f5.6. This is important as most kit zoom lenses have a focal ratio of f3.5-5.6, making the EF 50mm f1.8 II much better in low light.

It'll let you use faster shutter speeds or lower sensitivities than a kit zoom in low light, and deliver a much shallower depth-of-field for blurring effects. Mount it on a typical consumer Canon DSLR with an APS-C sensor and it'll also become a short telephoto that's ideal for portraits. This is why the EF 50mm f1.8 II is the natural choice as a second lens after a standard kit zoom. Couple all of this with the low price and it's understandable why the EF 50mm f1.8 II is Canon's best-selling lens. The AF performance and build quality may be very basic, but the optical quality is surprisingly good for the money - indeed it outperforms many more expensive lenses.
   
The full-frame Mark III allows us to compare the sharpness across the entire frame from the extreme corners to the center; by taking a carefully measured crop, we can also simulate the corner performance when mounted on a camera with a smaller APS-C sensor.

The Mark III was set to 100 ISO and the lens focused on the center of the composition using magnified Live View assistance. Most of the scene is effectively at infinity so even at f1.8 the depth of field covers the range of distances from top to bottom.   

I shot the scene in RAW and processed the files in Adobe Camera RAW using sharpening at 70 / 0.5 / 36 / 10, Luminance and Colour Noise Reduction both set to zero, and the Process to 2012 with the Adobe Standard profile; meanwhile the White Balance was manually set to 5500K. The high degree of sharpening with a small radius enhances the finest details without causing undesirable artefacts. I also switched off all lens corrections to reveal vignetting, chromatic aberrations and geometric distortions.

I also have a fourth and fifth page illustrating and comparing the depth of field and bokeh quality - you can jump to any of these from the index above right. Now it's time to discuss the results on this page, below, for the corner sharpness on full-frame cameras.

50mm f1.8 Bokeh

Like its more expensive counterparts, the Canon 50mm f1.8 II suffers from noticeable vignetting, softness and some coma in the corners. Most of the vignetting has gone by f2.8 though, and all but the extreme corners have sharpened-up too.

The image above right shows the full-frame area with three red rectangles representing the cropped areas on each results page. The crops presented on this page were taken from the red rectangle in the bottom left corner, so indicate the performance in the corner of a full-frame image.

50mm f2.8 Bokeh

There's a steady increase in sharpening as you close the aperture further, with the f5.6 result looking great and the f8 one cleaning up the extreme corners nicely. So if you'd like sharp results right into the corner of a full-frame sensor, you'll need to close the 50mm f1.8 to f5.6 or ideally f8.