Olympus E-M5 Optics

Zoom
A wider-than-average zoom range for a kit lens, with good performance.

The Olympus E-M5 is available bundled with an Olympus M.ZUIKO 12-50mm f/3.5-6.3 EZ Micro Four Thirds lens. The kit lens possesses an optical zoom ratio of about 4.2x, for a 35mm equivalent focal range of 24-100mm. Results were very good at 12mm, with strong detail and good contrast across the frame, though some softness and chromatic aberration can be seen in the corners. Sharpness and contrast was excellent across the frame at medium focal length of 27mm, with little chromatic aberration. Results were good at 50mm focal length, just slightly soft, but again with much lower levels of chromatic aberration. Overall, above average performance here for a kit lens. See below for comments on macro performance, geometric distortion, etc.

Macro
A small minium area, with very good detail. Flash exposure is dim.

As with zoom performance, the Olympus E-M5's macro performance will depend entirely on the lens in use. However, with the 12-50mm kit lens set to 43mm, the Olympus E-M5 captured a small minimum area for a kit lens, measuring only 1.40 x 1.05 inches (36 x 27 millimeters). Details were quite good, just a touch soft across the frame at f/8, and there's very little additional softening in the extreme corners. (Most lenses have some softening in the corners at macro distances, but the Olympus E-M5's kit lens has much less than most.) The bundled flash throttled down a bit too much at this close distance, resulting in a underexposed image.

Geometric Distortion
Low geometric distortion with the 12-50mm kit lens in JPEGs, much higher distortion in uncorrected RAW files.

When shooting JPEGs, the Olympus E-M5's 12-50mm kit lens produced about 0.3 percent barrel distortion at wide-angle, which much lower than average and only slightly noticeable in some of its images. At the telephoto end, there was almost no visible distortion, only about one pixel of barrel distortion. This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).

To see how much correction is taking place in the camera, we converted RAW files from the above shots with dcraw, which does not correct for distortion. As you can see, at wide-angle, the barrel distortion is very high at about 2.4%, while pincushion distortion at telephoto is a low 0.4%. We expect to see high distortion at wide-angle from smaller interchangeable lenses though, so it's nothing to be too concerned about unless you are using a RAW converter which does not understand the embedded "opcodes" to perform distortion corrections automatically. Most RAW converters these days are capable of applying distortion correction automatically, as specified by the manufacturer. There is however going to be some loss of resolution in the corners as a result of such correction, because pixels in the corners of the frame are being "stretched" to correct for the distortion. Obviously, a lens that doesn't require such correction that is also sharp in the corners to begin with would be preferable, but relaxing constraints on barrel and pincushion distortion likely brings other benefits in the lens design, such as cost, size and weight.

Chromatic Aberration and Corner Sharpness
Pronounced chromatic aberration in the corners at wide-angle; much lower levels at full telephoto. Some mild to moderate corner softening.

Chromatic Aberration. Chromatic aberration with the E-M5's 12-50mm kit lens was quite high and quite noticeable in the corners at wide-angle (12mm) when wide-open (maximum aperture), while the center showed very low levels. At full telephoto (50mm), C.A. was much lower, and not nearly as noticeable.  In both cases, the color fringing gradually reduces in brightness and width as it approaches the center of the image, where it is practically nonexistent.

The Olympus E-M5 does not appear to be reducing C.A. in its JPEGs, as uncorrected RAW files have similar amounts.

Corner Softness. The Olympus E-M5's 12-50mm kit lens produced some soft corners at full wide angle, though the center was very sharp. Left corners were fairly sharp, but right corners were soft, indicating some decentering. At full telephoto, the opposite (left) corners were soft while corners in the right-hand side were fairly shape, though the center was not quite as sharp as wide-angle. There's also some mild vignetting (corner shading) at wide-angle when wide-open, as indicated by the darker corner crop compared to the center.

Chromatic Aberration. With the aperture stopped down to f/8, chromatic aberration was still high, similar to wide-open.

Corner Softness. Corner sharpness improved slightly at wide-angle when stopped-down to f/8, but right-hand corners were still soft. Vignetting also improved to the point of being negligible. Corner performance improved at full telephoto with better contrast and sharpness, but were still a bit soft. The center was fairly sharp at f/8, though again not quite as sharp as wide-angle.

Shading Compensation
The Olympus E-M5 features optional Shading Compensation to reduce vignetting in JPEG images.

Mouse over the links above to compare thumbnails, and click on the links to load the full resolution images.

As you can see, the Olympus E-M5's Shading Compensation reduces corner shading with the 12-50mm kit lens, so it's a useful feature at wide-angle when shooting wide-open. There's little corner shading to correct at telephoto.

Shading Compensation is off by default, and is not available with all lenses. It may also produce more visible noise in the periphery at higher ISOs.

Accuracy
Very good accuracy from the EVF and OLED monitor.

The Olympus E-M5's electronic viewfinder and OLED monitor proved quite accurate in record mode, both showing about 101% coverage with our Olympus Zuiko Digital 50mm f/2.0 low distortion prime. Very good results here.