Panasonic G X Vario 12-35mm f/2.8 ASPH Lens Review
A great performer, but it doesn't exactly feel like a thousand bucks.
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 Panasonic G X Vario 12-35mm f/2.8 is designed to approximate what you'd get from a standard pro zoom, similar to the 24-70mm f/2.8 lenses you'd see on Canon or Nikon. While this lens is obviously more compact and not designed to compete directly with those (bigger, heavier, more expensive) lenses, it does have similar goals: chiefly, provide a lens that covers all standard focal lengths, a little bit of wide, a little bit of telephoto, and provide a constant fast aperture.
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.
While all zoom lenses strive to be as sharp as possible, the necessities of optical design often mean that zoom lenses are better in one area than others. Even pro-level lenses generally have to compromise somewhere. While the Panasonic 12-35mm has a little of this, it's actually surprisingly consistent through the zoom range.
At 12mm, 24mm, and 35mm we found a lens that was very sharp in the center from f/2.8 through f/8. At all three focal lengths we tested the center resolved over 2,000 lines at f/2.8, peaked at 2,100 to 2,200 lines from f/4 to f/5.6, and slowed to just under 2,000 lines at f/8. That's a remarkable performance given the limited resolving power of the 16-megapixel Olympus OM-D E-M1 sensor that we were testing with.
Off-center things are fine, but not nearly as rosy, but it depends on what focal length you're at. At 12mm the corner and midway regions both start around 1,200 lines, but sharpen up to about 1,500 and 1,600 lines respectively from f/4 to f/8. If you zoom in to around 24mm the corners never get above 1,250 lines, but the partway regions hover between 1,600 and 1,800 lines—not a bad result at all.
At full telephoto the whole frame is quite sharp from f/4 to f/8, with the center and partway regions rendering over 2,000 lines at their best while the corners top out at 1,550 lines. The only issue here is at f/2.8, where the corners are stuck at around 1,200 lines.
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.
Most zoom lenses that cover wide and telephoto focal lengths tend to have barrel distortion at one end that gives way to pincushion distortion. The Panasonic 12-35mm does suffer from distortion throughout the zoom range, but it's all pincushion distortion.
At all three focal lengths we tested we found 1% to 1.3% pincushion distortion in our test shots. This isn't ideal, but it's less than we expected and it's relatively easy to correct. Given that most similar zoom lenses exhibit as much as 3% barrel distortion on the wide end, this is a good effort from Panasonic.
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.
In general, there aren't any major chromatic aberration issues with the Panasonic 12-35mm f/2.8. It's visible in many scenes, but you do have to go looking for it and it's only truly visible in high contrast scenes near the edges. It's worst at the wide end than it is as you zoom in, but it's never worse than "minor" by our reckoning.
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”).
While the Panasonic 12-35mm f/2.8 doesn't produce the best bokeh that we've seen, it does well for itself. Backgrounds have a pleasing, smooth quality and these areas of the scene aren't marred by any notable flaws. Circular shapes remain so across the frame, though the lens doesn't render out of focus points of light with the crisp clarity that you'd get with the best portrait lenses.
You can see this in the samples above, where smooth backgrounds complement the crisp detail in the subject. In the first sample the lens takes a high-frequency scene with lots of contrast and specular highlights and keeps things relatively smooth. The second sample shows a few more jitters as the lens struggles to smooth out the black text and the straight lines of the copper pipes, but it's not offensive—especially for a zoom lens.
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