Shadow noise

Sony's sensors have gained a well-earned reputation for outstanding noise performance. In the comparison below we've taken Raw files and drastically opened up the shadows using Adobe Camera Raw (a beta version of 7.3) with sharpening and noise reduction turned off, to shine a light on the sensors' inherent capabilities. We've compared the SLT-A99 with three full frame rivals, the 24MP Nikon D600, the 22MP Canon EOS 5D Mark III and the 36MP Nikon D800. All three cameras were shot at ISO 100.

Sony SLT-A99 - ACR +3.0EV 100% crop
Nikon D600 - ACR +3.0EV 100% crop
Canon EOS 5D Mark III - ACR +3.0EV 100% crop
Nikon D800 - ACR +3.0EV 100% crop

As you can see, the A99 and Nikon D600 perform similarly, with the former showing a bit more chroma noise in the shadows and a perhaps marginally less detail in the spools of thread. The Canon EOS 5D Mark III is displaying noticeably more prominent chroma noise than the others, while the Nikon D800 shows off a resolution advantage that is accompanied by impressively little chroma noise.

Real world sample

While the results of our studio scene reveal interesting information about the sensor's maximum capabilities, it's important to place those results in the context of real-world photography. Below is an image shot outdoors under daylight conditions at ISO 100. We've made a side-by-side comparison showing the results of an .ARW raw file converted in ACR 7.3 with the in-camera JPEG at default settings.

Camera JPEG, default settings ACR 7.3 beta: Contrast +20, Shadows +50, Blacks +50 and CA correction
100% crop 100% crop

As you can see, the JPEG rendering blocks shadow details. In the custom raw conversion we were able to open the shadows with very little noise penalty and still maintain a pleasing overall contrast and exposure. The raw file simply has a lot of latitude for editing. Attempting to get similar shadow values in the JPEG file would lead to significant posterization, as there is not enough real data in the shadow areas to render usable detail.

In short, as we'd expect from looking at the Nikon D600's output recently, the A99's Raw images show an impressive ability to withstand luminance boosts in the shadows, revealing usable detail while keeping noise at very low levels. This level of shadow detail and noise suppression continues to be one of the biggest advantages of recent Sony sensors.

Overall image quality

The A99 produces very good JPEGs with reasonably sensible default settings. Unlike lower-end Sonys which can suffer from overly aggressive sharpening and noise reduction default settings, the A99 produces very usable files right out of the box. Color and contrast are reasonably accurate, with impressive white balance performance even under indoor mixed lighting scenarios. Metering is well judged in a wide variety of situations, with only backlit or very high contrast scenes requiring much use of the exposure compensation dial. It is with shooting Raw files, however, that the A99 really shines. The level of detail here is among the best we've seen from a 24MP sensor and the files provide significant headroom for retaining both highlight and shadow information.

Sony has made claims for improved noise performance with its latest 24MP sensor and circuitry design, and our experience looking over hundreds of high ISO files from the A99 backs this up. Chroma noise is well controlled up to ISO 6400 and even then, with a bit of careful processing, you can make pleasing prints from files even at the maximum ISO sensitivity.

One thing we do wish for is the ability to process Raw files in-camera, as we've seen on Nikon and now Canon DSLRs. While we suspect this is not at the top of most users' wish lists, this is a feature that can come in handy, particularly as Wi-Fi capable add-ons are becoming more common, enabling photographers to share images directly from the camera.