DxOMark review for the Sony Alpha 700

Tuesday, March 10, 2009

Camera Review
DxOMark review for the Sony Alpha 700

The Sony Alpha 700 with its new version 4.0 firmware scored a 66.3 on the DxOMark Sensor scale, putting it in 17th place on the dxomark.com overall ranking, and in 5th place for APS-C cameras. Given its launch date (Sept. 2007), this is a pretty good result.

When we first analyzed the Sony A700, our preliminary tests showed that it made use of green-channel RAW NR (Noise Reduction). To ensure fair ranking on dxomark.com, we only score cameras that do not exhibit any sort of spatial signal filtering, taking care to test every camera we report on. With the latest A700 firmware version (rev.4) that disables noise reduction on the green channel, it is then possible to publish all its measurement results and DxOMark ranking.

Key sensor characteristics

Sony acquired Konica Minolta’s DSLR division following the launch of Konica Minolta’s last high-end DSLR, the Maxxum 7D. Two years later, Sony came forward with the first high-end DSLR in its product line, the Sony Alpha 700. For this first “expert amateur” model, Sony replaced the old Alpha 100 model sensor for a new APS-C sensor with a resolution of 12.2 Mpix. For some time, the A700 made use of RAW noise reduction until the last delivered firmware, version 4.0, switched it off.

Key performance factors

With a Color Depth score of 22.3, Dynamic Range of 11.9 and Lowlight ISO of 581, the Sony Alpha 700 is in a good position among APS-C format leaders.

Noise reduction comparison: firmware version 1.0 vs firmware version 4.0

As published in the dxomark.com Q&A section, we test to ensure that our website provides data only on camera sensors which do not apply RAW spatial signal filtering. With respect to the Sony A700, we waited until the most recent release of its firmware (version 4.0) before subjecting it to our regular battery of RAW sensor tests.

Figure 1 below displays the results of DxO Labs’ signal filtering tests for the Sony alpha 700 (firmware version 1.0) , which showed a noise filtering reduction on the green channel. This noise filtering was not applied from ISO 100 to ISO 800, but became particularly strong in the dark from ISO 1600 to ISO 6400. Figure 2 shows DxO Labs’ signal filtering test results for the A700 using firmware version 4.0.

3D view green-channel
Figure 1. 3D view of the autocorrelation of the green channel for Sony A-700 (firmware version 1.0), ISO 6400, 10% grayscale. The expected peak had been smoothed by noise reduction filtering (which explains the larger base of the peak). This type of processing will impact the effective resolution by adding correlation between pixels, resulting in loss of detail.
3D view green-channel
Figure 2. 3D view of the autocorrelation of the green channel for Sony A-700, ISO 6400 (firmware version 4.0, 10% grayscale. As shown by the single peak (denoting white noise only), the A700’s noise reduction filtering has been switched off.

 
 
For further information on in-camera RAW signal processing, see the “Half-cooked RAW” insight.

Sony Alpha 700 DxOMark review – March 10, 2009