Sony RX10 III Optics

Zoom
A very generous 25x zoom for a 1"-type sensor, with excellent optical performance.

The Sony RX10 III is equipped with a 8.8-220mm lens, offering a zoom ratio of 25x for an extremely versatile 35mm-equivalent focal range of about 24-600mm. Like other recent Sonys, the RX10 III also offers Clear Image Zoom up to 2x and standard digital zoom up to 4x.

Maximum aperture is a relatively fast f/2.4 at wide angle that drops only 1.5 f-stops to f/4 at telephoto, already at about 100mm equivalent. The following table reflects the maximum and minimum apertures as reported by the camera at various focal lengths:

Far-field performance appears to be excellent at f/5.6, with very good sharpness and contrast across most of the frame across the zoom range, and only minor softening and coma distortion in the extreme corners. Chromatic aberration is fairly low (like most cameras, the RX10 III does a pretty good job at suppressing it), and flare appears to be reasonably well-controlled for such a long lens.

The above series is meant primarily to show zoom range so it isn't great for judging optical performance. See below for our lab results on macro performance, geometric distortion, corner and center sharpness, etc.

Macro
A slightly larger-than-average sized minimum coverage area, with very good detail. Flash worked fairly well at full telephoto, though exposure was a little dim.

The Sony RX10 III captured a slightly larger-than-average sized minimum area in Macro mode, measuring 2.67 x 1.78 inches (68 x 45 millimeters) at full telephoto, although that's quite good for such a long zoom. (Maximum reproduction ratio is specified as 0.49x at the tele end, versus 0.42x at the wide end.) Detail is excellent across much of the frame with corners only exhibiting a bit of softness at f/8 (most lenses show some softening in the corners at macro distances). At full telephoto the flash worked fairly well producing an evenly exposed though somewhat dim image, and the lens caused no shadow. (You'll likely get a lens shadow at wide angle, though.)

Geometric Distortion
Extremely low distortion in camera JPEGs, high in uncorrected RAW files.

Geometric distortion in JPEGs is extremely well corrected, with hardly a pixel's worth of barrel distortion at both maximum wide angle and at full telephoto. 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).

Unsurprisingly, uncorrected RAW files show fairly high geometric distortion. We measured about 2.6% barrel distortion at maximum wide angle, and about 1.1% pincushion distortion at full telephoto. That's not unusual, though, and most RAW converters should automatically correct for it, however strong correction can lead to some artifacts and additional softness in the corners.

Chromatic Aberration and Corner Sharpness
Very low to moderate chromatic aberration. The lens produced some soft corners, though corner sharpness improved stopped-down.

Chromatic Aberration. Lateral chromatic aberration in camera JPEGs is fairly well corrected, with only moderate amounts in the corners at both wide angle and full telephoto, and low amounts at intermediate focal lengths. The center shows very low levels of C.A. at wide and intermediate focal lengths but slightly higher levels at telephoto, though still low.

Corner Softness. Sharpness and corner performance are generally very good for the type and speed of lens, though our copy appears to have a slightly decentered element or group (unfortunate, but not at all unusual). In our sample, at 24mm eq. and at maximum aperture (f/2.4), the top right corner is the softest while the other corners are better but still a bit soft, however the center is tack sharp, and what corner softness there is doesn't extend far into the frame. At 70mm equivalent, the lens isn't quite as sharp in the center wide open as at 24mm eq., but it's still pretty sharp, and corners are just slightly soft. At 200mm eq., the lens is remarkably sharp across the frame wide open. At 600mm equivalent, the bottom right corner is soft while the other corners are slightly better. The center is fairly sharp wide open, though likely not quite as sharp as maximum wide angle. (Be aware that our telephoto target for long-zoom cameras like the RX10 III is smaller than our wide-angle target, so resolution between wide and tele isn't directly comparable. Also note that the corner USAF resolution chart in our long-zoom telephoto target isn't in the extreme corners for 3:2 cameras like it is for 4:3 cameras.)

Vignetting. As you can see from the darker crops, there's some moderate corner shading ("vignetting") at full telephoto wide open, but less at shorter focal lengths.

Stopped-down: Stopping down to f/4.0 at 24mm equivalent improved corner sharpness and chromatic aberration slightly, but corners are still not as sharp as the center, and the center itself isn't quite as sharp as wide open though it's still very sharp. Stopping down to f/5.6 at 70mm eq. reduced chromatic aberration in the corners and improved corner softness significantly, though again, the center isn't quite as sharp as wide open. There is also a slight reduction in sharpness at 200mm equivalent at f/5.6 compared to wide open, though it's still quite sharp across the frame, and vignetting was reduced as well. At full telephoto the center remained about the same stopped down to f/5.6, however sharpness, CA, as well as vignetting all improved in the corners, though they are still a bit soft. Stopping down past f/5.6 generally does help a bit more in soft corners, however diffraction becomes stronger, softening the image elsewhere.

Chromatic Aberration Correction. As mentioned previously, lateral chromatic aberration in camera JPEGs is fairly well corrected, with moderately low to moderate amounts in the corners. As you can see from the uncorrected RAW crops (above right), lateral chromatic aberration is actually quite high and bright at maximum wide angle when wide open, and a little higher at full telephoto wide open (the worse-case scenarios), so the Sony RX10 III's processor does a good job correcting for most of it in JPEGs.

Overall, excellent performance for a relatively fast 24-600mm equivalent f/2.4-4 lens.

Coverage
Excellent accuracy from the electronic viewfinder and LCD monitor.

The Sony RX10 III's electronic viewfinder and LCD monitor both showed just over 100% coverage at wide angle and at full telephoto, which is excellent, especially given the amount of geometric distortion correction being applied.