Our new Dynamic Range measurement system involves shooting a calibrated Stouffer Step Wedge (13 stops total range) which is backlit using a daylight balanced lamp (98 CRI). A single shot of this produces a gray scale wedge from (the cameras) black to clipped white (example below). Each step of the scale is equivalent to 1/3 EV (a third of a stop), we select one step as 'middle gray' and measure outwards to define the dynamic range. Hence there are 'two sides' to our results, the amount of shadow range (below middle gray) and the amount of highlight range (above middle gray).
To most people highlight range is the first thing they think about when talking about dynamic range, that is the amount of highlight detail the camera can capture before it clips to white. Shadow range is more complicated, in our test we stop measuring values below middle gray as soon as the luminance value drops below our defined 'black point' (about 2% luminance) or the signal-to-noise ratio drops below a predefined value (where shadow detail would be swamped by noise), whichever comes first.
Dynamic Range Optimization feature
Having seen an evolution of Sony's Dynamic Range Optimization feature in the A700, it's a bit of a shame (though understandable, at this price), to see the return of the rather more basic options seen on the A100.
There are two modes of DRO - Standard and Advanced Auto. In standard mode, the camera will try to reduce the contrast of the image when it identifies very high contrast in the scene being shot. This tries to ensure that the highlight and shadow detail aren't all pushed to white and black and that image more accurately represents what the photographer saw. Advanced Auto takes this a little further and, upon being confronted with a contrast with extremes of light and shade, tweaks the brightness and gradation in different parts of the image to give a balanced result. This second option is much more like Nikon's "D-lighting" feature. (And this isn't surprising, since both manufacturers state that their features use technology from the company Apical).
However, we've found it quite hard to provoke the system to activate, despite intentionally trying to photograph scenes with extremes of light and shade. On the occasions it did kick-in, the Advanced Auto mode gave the best results - lifting detail out of the shadows to give a brighter, more interesting image, without descending into 'first play with PhotoShop' HDR tone mapping ugliness.
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, instead giving two sliders to control its effects on shadows and highlights.
|DRO Advanced Auto|
Since there's no terrible performance disadvantage to leaving DRO in Advanced Auto mode (which appears to give the best results), so we'd be inclined to leave it turned on, on the basis that it doesn't appear to do any harm and will, from time-to-time, improve the output images.