Noise, Resolution and Sensitivity
With a large, high-resolution sensor and bright lens, we would expect the Sony Cyber-shot DSC-RX100 to do very well against its competition. Despite its high resolution, the size of the sensor means that the photosites are a claimed 3.6x larger than those in the company’s own Cyber-shot HX20V. For resolved detail, the RX100 does not disappoint, and raises the bar for other pocket cameras to follow. Impressively, detail is largely uncompromised throughout the ISO sensitivities for well-exposed images.
Image: This image at a train station is shot at ISO 800. The unedited raw file shows more luminance noise than the JPEG, but there is more detail in the shadow areas and it is not as ‘mushy’
Our resolution charts indicate centre sharpness, and JPEG files reach the 26 marker at ISO 100, dropping only to the 24 marker at ISO 3200. To get the most out of the camera, however, it is necessary to use raw format, because the camera resolves up to the 28 marker on our charts, which is the most detail we have seen from any pocket camera. There is a fall-off in sharpness of edge detail, certainly at the widest focal length, but not to any unacceptable levels.
In general, JPEG compression is much more aggressive in compact cameras than in DSLRs. The RX100’s noise reduction and sharpening adjustments are more obvious than the colour adjustments in JPEG compression, especially at ISO 1600 and higher where detail is much more ‘mushy’.
Therefore, in low light it is worthwhile shooting in raw format. I was particularly keen to see the quality of detail in real-world images, such as landscapes, and I was impressed by the crispness of detail, such as blades of grass, when an ISO setting of 400 or below is used. The selected aperture also makes a difference to sharpness, with f/4-5.6 the optimum setting.
The native ISO range can be extended from ISO 125-6400 to 80-25,600, the high setting available only in multi-frame NR mode. Handling of noise is good if not spectacular, with luminance and chroma noise faintly noticeable in real-world images at ISO 400 and more obvious at ISO 800.
Images all the way to ISO 1600 are perfectly usable, however, even up to ISO 6400, especially given that the large file size of full-resolution images means that noise is less noticeable when viewing an RX100 image at the same size as a one taken from a lower-resolution camera. Having taken a few images in the multi-frame NR mode at ISO 25,600, I opted not to use it again as the smoothing of detail is particularly unpleasant.
Resolution charts: These images show 72ppi (100% on a computer screen) sections of images of a resolution chart, captured with the lens set to approx 50mm and f/5.6. We show the section of the resolution chart where the camera starts to fail to reproduce the lines separately. The higher the number visible in these images, the better the camera’s detail resolution is at the specified sensitivity setting.
