The fixed Carl Zeiss Sonnar T* 35mm F2 lens is obviously at the heart of the RX1's imaging system. We've therefore collaborated with DxOMark to bring you studio test data of the optics; as usual, you can also compare it to a range of other 35mm lenses in our our lens data widget. The RX1's lens is impressively sharp, even at F2; in fact it's very close indeed to the remarkable Sigma 35mm F1.4 EX DC HSM. Its only real flaw is visible vignetting even when stopped down, although this can be corrected in post-processing when necessary.
Note: it's not possible to determine the T-stop for a fixed lens camera, so this number is not displayed.
|Sharpness||Central sharpness is extremely high at F2, and the corners aren't far behind. As we'd expect they sharpen up on stopping down, and the very best results are obtained between F5.6 and F8, much as we'd expect on full frame. The image softens due to diffraction at the smallest apertures, but F22 will still be eminently usable when you need the depth of field.|
|Chromatic Aberration||Lateral chromatic aberration is very low. There's a little red/cyan fringing at the edges of the frame, turning to magenta/green in the corners, but you'll have to look quite hard to see it.|
|Vignetting||Vignetting measures 1.7 stops wide open, which is about par for the course with a 35mm F2 lens on full frame. Stopping down to F2.8 reduces this 1 stop, but unusually the figure then hovers around this mark as you stop down further, meaning there's still visible vignetting even at F8-11.|
|Distortion||The RX1's lens shows noticeable barrel distortion - at 1.9%, it's a bit more pronounced than you'd get from a highly-corrected SLR lens. The pattern is complex, meaning you'll ideally need to use software that's profiled for the RX1 to fix it completely.|
The RX1 has a specific macro setting, accessed by turning the middle control ring on its lens. This switches the minimum focus distance down to a nominal 0.2m (compared to 0.3m in normal shooting), but also limits the furthest focus to 0.35m.
Close-range image quality is pretty impressive. At F2, central sharpness is already very high, such that it barely improves on stopping down. In our flat-field chart test the corners are soft wide open, most likely due to curvature of field, but they sharpen up nicely by F5.6. There's just a little red/cyan lateral chromatic aberration at the corners of the frame, but nothing too objectionable. Barrel distortion is pretty strong, but can of course be corrected in-camera or in post-processing when necessary.
We wouldn't usually consider 35mm as an obvious focal length for close-ups, but have to give credit to Sony for providing the option. However in the unlikely event that you're buying a fixed lens compact with a semi-wideangle lens with an eye to shooting closeups frequently, it's worth knowing that the Fujifilm X100(S) offers closer focusing and higher magnification.
The lens test data in this review is produced in collaboration with DxOMark. Click here for the full test data over on dxomark.com