Sony RX1 Optics

Fixed 35mm lens
Excellent performance from the 35mm f/2 Carl Zeiss fixed lens.

The Sony RX1 is equipped with a fixed Carl Zeiss-branded 35mm f/2 lens, and since the RX1 has a full-frame sensor, there is no "crop factor." Construction consists of 8 elements in 7 groups, with a 9-bladed diaphragm providing a minimum aperture of f/22.

Sharpness and contrast are excellent at f/8 across most of the frame, and chromatic aberration isn't an issue in these images since the camera suppresses it (see below). Performance in the corners is very good, with just a hint of softening and very little coma distortion. See below for comments on macro, geometric distortion, performance wide open, chromatic aberration, etc.

Digital Zoom
The Sony RX1 offers three types of digital zoom which should come in really handy for a wide-angle fixed-focal-length camera. Sony's new Clear Image digital zoom is available with up to 2x magnification, standard digital zoom up to 4x, and Smart Zoom is available where the camera crops away the unused portion of the image when a lower resolution is selected. You can combine the various zooms as well, but maximum total zoom is 4x at full resolution increasing to 9.1x at the small image size (4.6MP). There are also 1.4x and 2.0x "digital teleconverter" modes which just crop the full-res image.

Clear Image zoom does a decent job at 2x magnification, though there's still a noticeable loss of fine detail and some visible aliasing artifacts, despite Sony's claim of being "nearly equivalent" to optical zoom. 2x Clear Image zoom combined with 2x standard digital zoom shows fewer aliasing artifacts than just 4x standard digital zoom, but results are also softer with lower contrast. It's probably best to avoid using digital zoom altogether and instead crop, upsize and sharpen as required during post processing, as the RX1's 24 million high-quality pixels offer a lot of latitude when it comes to cropping.

Macro
A larger-than-average minimum coverage area, with excellent detail. Flash exposure is uneven and dim.

The Sony RX1 captured a fairly large minimum area measuring 5.33 x 3.55 inches (135 x 90 millimeters) in Macro mode. Detail is excellent over most of the frame at f/8, while corners and edges are just slightly soft. (Most lenses have some softening in the corners at macro distances.) The flash throttled down a bit too much, and coverage is offset to the upper-left quadrant, leaving the bottom and right sides quite dark. Overall, the flash image is dim and unevenly exposed, so plan on using external lighting for macro shots at closer distances.

Geometric Distortion
About average geometric distortion.

The Sony RX1's lens produces about 0.7 percent complex barrel distortion, which is about average for cameras we've tested, including those with zoom lenses. Distortion is slightly asymmetrical though, which could make perfect correction more difficult. 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).

Note that the Sony RX1 offers in-camera Distortion Correction for JPEGs. See below for details.

Chromatic Aberration and Corner Sharpness
Low to moderate levels of CA (the camera suppresses it). The lens produces pretty sharp corners even when wide open.

Chromatic Aberration. Chromatic aberration in the corners is moderate and somewhat noticeable in these shots, especially with shading correction applied which lightens corners significantly when the lens is wide open (see below). The center of the image shows almost no CA. Stopping-down to f/8 helps reduce the appearance of CA in the corners, though it's still slightly visible.

Corner Softness. Wide open at f/2, the RX1's lens is quite sharp across the frame, with only very minor softening in the corners. There's some loss of contrast in the corners, but that's also likely due to the shading and CA correction applied (see below). When stopped down to f/8, corners have better sharpness and contrast, but are still just a hair softer than center which is very sharp. Still, exceptional corner performance for a 35mm full-frame lens.

Corner Shading. There's very little corner shading ("vignetting") in JPEGs, as the Sony RX1 corrects for it by default (see below). We measured about 1/3 EV of fall-off in the corners at f/2, falling to about 1/4 EV at f/8. You can however see hints of the "tint issue", where Sony's lens shading correction produces a subtle cyan-to-red color tint across the frame. More on that below.

Lens Corrections

The Sony RX1 includes the ability to automatically correct for geometric distortion, chromatic aberration, and lens shading (vignetting), as images are captured.

Geometric Distortion

Above, you can see with Distortion Correction enabled, the lens shows significantly less geometric distortion (~0.1% versus ~0.7%) in JPEGs, though edges are cropped away in the process. Because distortion wasn't very symmetrical to begin with, the corrected image shows some pincushion on the left vertical edge, while the right still shows some barrel distortion. The default Distortion Correction setting is Off.

Chromatic Aberration

As you can see, lateral chromatic aberration is higher and much brighter with Chromatic Aberration Correction disabled, so the Sony RX1 does a pretty good job at eliminating most of it in JPEGs. The default for this setting is Auto.

Lens Shading

Mouse-over the links above to see the difference Lens Shading Correction makes when wide-open at f/2 (the worst-case scenario). The default setting for this correction is Auto, which means the camera will apply Shading Correction depending on the current aperture and perhaps other shooting conditions.

As you can see, corners are brightened significantly without affecting brightness at the center, so lens shading is quite pronounced at maximum aperture. (We measured just under 1 EV of fall-off in the corners at f/2, and just over 1/2 EV at f/8.) The corrected image does however exhibit a slight cyan tint on left side shifting to a slight red tint on the right side of the frame, which is not present in the uncorrected image. We've found that corresponding raw files have this tint as well, so it appears Sony is baking lens shading correction into RX1 raw data. Hopefully Sony will release a firmware fix to address this anomaly, though we haven't received confirmation from the company on this issue yet. In the meantime, we recommend shooting with Shading Correction disabled and correcting corner shading in software. See this news article for more details on the Sony RX1 shading correction tint issue.

Overall, though, excellent performance from the Sony RX1's 35mm f/2 lens, and it's nice to be able to individually control the application of available lens corrections.

Coverage
Excellent accuracy from the LCD monitor.

The Sony RX1's LCD monitor shows essentially 100% coverage. This is excellent performance, though not a surprise given its image is derived from the main imaging sensor.

The optional FDA-V1K optical viewfinder is a little loose with about 103% coverage in our test, so we captured slightly less than what we saw. Coverage will vary with distance to the subject, though. The optional FDA-EV1MK electronic viewfinder is however quite accurate, at about 100% coverage.