Dynamic Range Optimizer (DRO)
The Alpha 900 features an upgraded version of Sony's now ubiquitous D-Range Optimizer (apparently the algorithms have been improved). As with other systems (many of which are also based on technology developed by Apical) this uses clever processing to apply a complex tonal correction based on an analysis of the scene contents. The result is akin to the old Photoshop technique of 'contrast masking' (lifting shadows without burning out highlights), and at its strongest setting can produce results that veer dangerously close to 'fake HDR' territory.
There are four DRO options:
- Off: The camera carries out no dynamic range optimization.
- D-R Standard: The camera optimizes the image by automatically adjusting the tone curve used to the linear RAW data into the final image (hence the brightness / contrast).
- Advanced Auto: The camera optimizes the image by selectively adjusting the brightness of areas of the image, it 'masks' certain areas for lightening, others are darkened slightly. This can be thought of as a digital 'dodge and burn'.
- Advanced Level: As above with user-selected level (strength) from Lv1 (weak) to Lv5 (strong).
DRO doesn't appear to to interact with the camera's exposure metering, so it makes no additional attempt to retain highlight information - it's all about the shadows. As a result, users who shoot exclusively in RAW mode will not see any effect of DRO (it's a post-shot processing step so it only appears in JPEGs). The included software doesn't allow you to simply apply the same DRO effects to RAW files (it doesn't offer the 'advanced' option at all), but it does offer an auto setting as well as manual sliders for strength and highlight/shadow balance.
As the examples below clearly show, as you ramp up the Advanced DRO you can bring back an incredible amount of shadow detail (which does of course bring with it noise issues), though unless you manually reduce the exposure it can't do anything for clipped highlights.
DRO options: studio comparison
In the comparison below the exposure has been kept the same (it's fixed so that the 18% grey card in the illuminated area sits at mid-grey (L50), all we've changed is the DRO setting. As you can see DRO doesn't really touch the highlights, but brightens shadows by an increasing amount as you increase the setting. In most cases the Standard setting doesn't do a lot. The only negative consequence of using a higher level of DRO Advanced is an inevitable increase in shadow noise - this is particularly problematic at higher ISO settings (where the shadow noise is normally masked by the default tone curve).