Andy Westlake tests Sigma’s unconventional SA-mount mirrorless camera, the sd Quattro
Sigma sd Quattro review: Super Fine Detail Mode
One potentially useful new feature on the sd Quattro is its SFD mode. This takes seven bracketed exposures in 1-stop steps from a single press of the shutter, covering an overall range of ±3EV. These are then combined into a single X3I raw file – essentially seven concatenated X3Fs – and saved together. The idea is that by bracketing so widely, the camera should record a full range of detail from bright highlights to deep shadows, which can then be brought out in post-processing without excessive noise appearing. In essence, this makes up for the sensor’s relatively limited dynamic range.
As with other multi-shot modes, you have to lock the camera down on a tripod to ensure it doesn’t move between exposures – anything moving in the scene could cause problems. Sigma automatically sets the ISO to 100, and it makes sense to use the 2sec self-timer to avoid vibrations. The resultant X3I files are vast – almost 370MB – and can’t be processed in-camera, only using Sigma Photo Pro. This turns out to be the biggest problem, as developing them takes forever. By default, files are output in a minimally processed state with low contrast, saturation and sharpening, presumably on the basis you’ll work them up further.
However, in favourable situations SFD mode can bring clear benefits; in the example above I used it to record detail in a bright sky and dark foreground that the sensor simply couldn’t capture in a single exposure. But like other multi-shot modes, it’s not very convenient to shoot or process.