Sony SLT-A57 Review

Monday March 19 2012

Sensor Review
Sony SLT-A57 Sensor performance | Introduction | Sony SLT-A57 Preview
Sony SLT-A57

The results achieved by the Sony SLT-A57 are very close to those obtained by the other SLT reflexes endowed with the same sensor. This Exmor CMOS sensor once again distinguishes itself on this camera with excellent image quality, a very comfortable dynamic range score of 13EV, and a very honorable low-light ISO score of 785, which allows the Sony SLT-A57 to be used at high sensitivities without a second thought. Even though it has the same sensor as its predecessor, the SLT-A55, the SLT-A57 pushes the maximum sensitivity from 12,800 to 16,000 ISO.

The Sony SLT-A57’s DxOMark general rankings

  • Overall score (28th place)
  • Color depth (30th)
  • Dynamic range (14th)
  • Low-light ISO (48th)

The cost of Sony SLT technology: one-half diaphragm

Ranked only 28th among all tested cameras, the Sony SLT-A57 could have done better — at least, its 16Mpix APS-C CMOS sensor is better than the measurements suggest. It so happens that the translucent mirror technology that Sony uses in its SLRs diverts a portion of the light that is captured by the sensor in other, more conventional cameras (see our explanation of the SLT system in our analysis of the SLT-A77). As with other Sony cameras that use its “Translucent Technology,” the SLT-A57 loses a demi-diaphragm when compared to, for example, the Nikon D7000 or a compact hybrid whose sensor captures all of the light. Depending on their habits and priorities, photographers may need to take into account this loss of sensitivity. If they are most concerned about image quality at high sensitivities, they should note that SLT-A57 is surpassed by the NEX-C3 (since replaced by the NEX-F3) and the NEX-5N (to stay in the Sony family).

Sony SLT Alpha 57 vs Sony NEX-5N vs Sony NEX-C3

With respect to its siblings equipped with the same sensor, the SLT-A57’s sensitivity range amplitude is very respectable:

  • The most extensive is the Sony NEX-5N (from 100 to 25600 ISO).
  • The least extensive is the Sony NEX-C3 hybrid (from 200 to 12800 ISO, but its replacement, NEX-F3, has the same amplitude as that of the A57 reflex, from 100 to 16000 ISO).
Sony SLT Alpha 57 vs Sony NEX-5N vs Sony NEX-C3: SNR comparison
Sony SLT Alpha 57 vs Sony NEX-5N vs Sony NEX-C3: SNR comparison.

A more advanced Sony 16Mpix APS-C sensor?

Sony outclasses the competition with its latest Exmor sensors — the 16Mpix CMOS APS-C used in the SLT-A57, the 24Mpix sensor used in the NEX-7 and the SLT-A77, and the specially-designed 36Mpix Full-Frame sensor used in the Nikon D800 — all of which are based on the same technology, with widely-recognized success: at 95 points, the D800’s sensor holds the record to beat for best DxOMark score. This all said, the SLT-A57’s CMOS sensor that came out this spring didn’t bring with it any improvements: in fact, it is exactly the same sensor that came out two years ago. We were rather expecting the arrival of a 16Mpix APS-C Exmor “Mark II” sensor for cameras belonging to the 2012-2014 generation.

Sony SLT Alpha 57 vs Canon PowerShot G1X vs Canon EOS Rebel T3i, EOS 600D

This advanced amateur SLR, currently a top choice among photographers, competes against the Canon EOS 600D, which also reuses a sensor — the even older 18Mpix APS-C CMOS sensor first used in the EOS 7D nearly four years ago. We’ve seen this very same sensor in reviews of the latest Canon cameras, whether the Powershot G1 X compact, the Canon EOS 600D, or the Canon EOS 5D Mark III, and the bottom line is that Canon’s sensor technology has hardly made any progress at all. The comparative measurements of the Sony SLT-A57 vs Canon EOS 600D and Powershot G1 X cannot be refuted— Sony sensor technology clearly exceeds the performance of Canon cameras for all criteria measured:

  • For color depth: 1.3bit (vs the 600D) and 1.6bits (vs the G1 X);
  • For low-light image quality from 100 to 400 ISO and from 6400 to 16000 ISO (see the CS curves);
  • For dynamic range: 1.5EV more than the EOS 600D and 2.2EV more than the Powershot G1X.

As shown in the dynamic range / sensitivity curves for the three sensors, the dynamic range of the Canon cameras stagnates below 400 ISO. By contrast, the Sony continues to progress until it reaches 13.02EV at 100 ISO (whereas the EOS 600D plateaus at 11.46EV at 100 ISO).

Sony SLT Alpha 57 vs Canon PowerShot G1X vs Canon EOS Rebel T3i, EOS 600D: Dynamic range comparison
Sony SLT Alpha 57 vs Canon PowerShot G1X vs Canon EOS Rebel T3i, EOS 600D: Dynamic range comparison


Despite the lack of evolution in the Sony 16 Mpix sensor, the SLT-A57 shines compared to its Canon competitors, with performance levels a clear notch above. Although its performance is slightly below that of the NEX hybrids and other conventional SLRs, the cost of the A57’s SLT technology (a demi-diaphragm) is the price one must pay to benefit from its burst shooting rate of up to12 i/s, its phase-detection video autofocus, and its EVF WYSIWYG viewfinder — of particular interest to those left cold by traditional SLR optical viewfinders.