Canon EF 24-70mm f/2.8L II USM Lens Review
Sharp, fast, compact, and durable—this lens is a pro's best friend.
When evaluating any lens, we focus on four key areas: sharpness, distortion, chromatic aberration, and bokeh. A perfect lens would render the finest details accurately, wouldn’t distort straight lines or produce ugly fringing around high-contrast subjects, and would create smooth out-of-focus areas.
The updated Canon EF 24-70mm f/2.8L II is a much sharper lens than most other zooms. It has some issues with chromatic aberration, and the bokeh (while generally excellent) has a few quirks, but they're all minor. There's a reason that this lens is so revered; it's spectacular, with a strong performance profile across the focal range.
A lens's sharpness is its ability to render the finest details in photographs. In testing a lens, we consider sharpness across the entire frame, from the center of your images out to the extreme corners, using an average that gives extra weight to center performance. We quantify sharpness using line widths per picture height (LW/PH) at a contrast of MTF50.
At 24mm, sharpness peaks at f/2.8, hitting roughly 2,450 lines right from the get go. From f/2.8 through f/8, center resolution stays above 2,000 lines, then falls off rather dramatically once the diffraction limit kicks in. Midway areas start at just 1,650 lines at f/2.8 before jumping above 2,000 lines from f/4 to f/8. The corners are (predictably) the softest part of the frame, starting at just 1,250 lines at f/2.8. They improve gradually as you stop down, peaking at f/8 and 1,825 lines.
You'll find a similar performance profile as you zoom in, though the corners don't improve quite so much. At the midpoint of the zoom range, the center and midway peaks are nearly identical, but the corners only get up to 1,600 lines at f/8 and f/11. The telephoto end sees almost no improvement in the corners, with resolution between 1,100 and 1,300 lines regardless of aperture. The center performance at 70mm is also slightly lower, though still excellent—a bit above 2,000 lines at f/2.8, hitting 2,200 lines by f/5.6.
We penalize lenses for distortion when they bend or warp images, causing normally straight lines to curve.
There are two primary types of distortion: When the center of the frame seems to bulge outward toward you, that’s barrel distortion. It's typically a result of the challenges inherent in designing wide-angle lenses. When the center of the image looks like it's being sucked in, that’s pincushion distortion. Pincushion is more common in telephoto lenses. A third, less common variety (mustache distortion) produces wavy lines.
Though the 24-70mm goes quite wide, it does a respectable job of keeping geometric distortion to a minimum. At 24mm, the usual barrel distortion is present, but it peaks at just 0.5%—hardly noticeable. As you zoom in, barrel turns to pincushion. At the midpoint it's still negligible, though by 70mm it jumps to around 1.8%. You'll see it in some straight-out-of-camera shots, but it's easy enough to correct in your photo editor of choice.
Chromatic aberration refers to the various types of “fringing” that can appear around high contrast subjects in photos—like leaves set against a bright sky. The fringing is usually either green, blue, or magenta and while it’s relatively easy to remove the offensive color with software, it can also degrade image sharpness.
The EF 24-70mm f/2.8L II is superb in many respects, but CA resistance isn't one of them. In our testing, aberrations were worst at f/2.8 and 24mm. There, CA peaked at around 0.14% on average—enough to be noticeable in high-contrast scenes. As we'd expect, it's worst in the corners, and likely plays a role in the weak corner resolution at f/2.8. As you zoom in, the CA slowly goes away. That's good news if you prefer portraits to architecture.
Bokeh refers to the quality of the out of focus areas in a photo. It's important for a lens to render your subject with sharp details, but it's just as important that the background not distract from the focus of your shot.
While some lenses have bokeh that's prized for its unique characteristics, most simply aim to produce extremely smooth backgrounds. In particular, photographers prize lenses that can produce bokeh with circular highlights that are free of aspherical distortion (or “coma”).
The Canon EF 24-70mm f/2.8L II USM exhibits excellent bokeh in most situations, though it's best at 70mm. The lens renders out-of-focus areas smoothly, with very little aspherical distortion or coma wide open. Some high-frequency backgrounds can look a bit "busy" (seen in the sample below), but it's not a big deal.
The biggest issue we ran across in our test shots was that out of focus points of light, while rendered as large, circular orbs, also had some of the nastiest "onion ring" texturing that we've come across.
That's typical of lenses that feature aspherical elements, though some more recent designs from other manufacturers have taken steps to address the problem. It's not that noticeable in many shots, but if you sharpen your photo in post (even with local contrast adjustments like Lightroom's "Clarity" slider) you'll often amplify the rings along with all the other details.
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