The Canon EF 50mm f/1.2 L USM, (compare prices), is the current premium 50mm lens. It’s larger, faster, heavier and much more expensive than any of the other production lenses.
As you would expect from an “L” series lens, it’s sturdily constructed and has an optical design of 8 elements in 6 groups, with a large rear aspherical element made of high refractive index glass to minimize aberrations.
Brief Specifications
Focal Length 50mm Maximum Aperture f/1.2 Lens Construction 8 elements in 6 groups Diagonal Angle of View 46° (with full-frame cameras) Focus USM with full-time manual Closest Focusing Distance 1.48 ft. / 0.45m Filter Size 72mm Max. Diameter x Length, Weight 3.4 in. × 2.6 in./85.4mm x 65.5mm
19.2 oz./545g (lens only)
Given that marked apertures are only approximate and small fractions of an f-stop are insignificant, you can take it that an f/1.2 lens is 1/2 stop faster than an f/1.4 lens and 1 stop faster than an f/1.8 lens.
Image Quality
Most of the examples in this section will compare the 50/1.2L with the 50/1.8 because those are the two 50mm prime lenses I had available to compare. The 50/1.8 is 20 years old and is the original version with the metal mount. The current version, the EF 50/1.8 II, uses identical optics but mounted in a different (all plastic) body.
Bob Atkins
I ran a number of tests including shots of resolution test charts and “real world” images, so my comments are based on looking at dozens of different images, not just the few samples shown here. Unless specifically stated otherwise, all comments and image samples relate to full frame images taken with an EOS 5D.
Fast lenses shot wide open are often a little soft. This softness usually results mainly from spherical aberration which is difficult to eliminate in fast lenses. Spherical aberration diminishes rapidly as a lens is stopped down, so closing down even as little as 1/3 stop or 1/2 stop can make a noticeable difference.
Bob Atkins
The 50/1.2L is pretty sharp wide open at f/1.2, though when you compare it with images taken stopped down to f1.4, f1.6 and f1.8 (see images above on right), you can see that the wide open shot is a little softer.
Real world shots taken at f/1.8 with the 50/1.2L and the 50/1.8 show that the 50/1.2L is clearly sharper (see 100% crops on right), but by the time that both lenses are stopped down to f2.8, the difference in the images (in the center of the frame) becomes pretty small.
At the edge the 50/1.2L shows better contrast and sharpness than the 50/1.8 through about f/4. Overall I’d say that the 50/1.2L peaks at about f/4 in the center of the frame and about f/5.6 at the edges.
Bob Atkins
Under adverse lighting conditions the flare control of the 50/1.2L is very good and contrast is well maintained. On the right is a comparison between the 50/1.2L and 50/1.8 showing the image quality of the corner quality of a full frame image at an aperture of f/2.8. The 50/1.2L clearly shows the higher quality image, especially in terms of image contrast and flare suppression.
Image distortion is low with any of the 50mm prime lenses, so it’s really not a factor in deciding between them. The 50/1.2L shows a very small degree of barrel distortion which is unlikely to be noticed in real world images. One area in which the 50/1.2L may not excel is CA. There is a slight amount of lateral chromatic aberration (CA) visible. Though it’s slight and unlikely to cause problems, the CA of the 50/1.8 is even smaller. Of course if you shoot RAW and use DPP to convert the image to a JPEG, you can automatically correct the image for CA as well as distortion and vignetting.
Background Blur and Bokeh
Bob Atkins
The fast aperture of the EF 50/1.2L USM, when shot wide open, results in a small depth of field and a large amount of background blur. At smaller apertures DOF is larger and background blur is reduced, but the quality of the blur (“bokeh”) is maintained due to the use of an 8 blade circular aperture which keeps out of focus highlights looking round rather than, for example, the hexagonal blur pattern from a simple 5 blade aperture (see illustration on right).
Bob Atkins
Bokeh can be a very subjective concept and is very hard to quantify. The nature of the background blur depends on the aperture shape, the optical design of the lens, the focus distance and the distance to the background (or foreground) which is out of focus. A lens which has very pleasing bokeh at one set of distances might have harsh boken at others (e.g. when focused very close).
Vignetting
Despite the fact that the 50/1.2L is a large lens with a large filter size, it’s by no means immune from vignetting. Few, if any, fast lenses are.
Bob Atkins
On a full frame camera, wide open, the corners are about 2 1/3 stops down on the center and the edges are about 1 2/3 stops down. This is pretty much what you might expect from any lens of this type. Stopping the lens down evens out illumination pretty quickly and by f/2.8 vignetting is pretty much gone (1/2 stop in the corners, 1/3 stop at the edges).
The illustration on the right shows relative vignetting of the 50/1.2L and the 50/1.8 at f/1.8 on a full frame sensor. An outline is also shown for the area covered by an APS-C sensor and you can see that vignetting is much reduced on the crop sensor.
f/1.2 corner/edge f/1.8 corner/edge f/2.8 corner/edge EF 50/1.2L USM 2.33/1.67 1.5/0.67 0.5/0.33 EF 50/1.8 II - 2.25/1.75 1.25/0.5
