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Dynamic range

Our 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.

At default settings

Using its standard settings, the S100FS behaves as we'd expect - it can't quite compete with most DSLRs in the highlight region but shows a pretty respectable 9.2 stops of range in total. The total range drops as sensitivity is increased because the dark areas of the image become increasingly noisy and are clipped by our analysis tool.

It's worth noting that whilst the 'total' range is good, the curve shows there is virtually no 'roll off' at the highlight end (something common to most compact cameras), meaning at about 3.0 EV above 'middle grey' the S100FS will clip pretty harshly. Most digital SLR's provide more reach in the highlights and offer a smoother roll-off. Conversely the excellent shadow reach can at least in part be attributed to a fairly aggressive approach to noise reduction (again something common in compacts).

Extended dynamic range

That isn't quite the end of the story for the S100FS, though. Unusually for a non-SLR, the Fuji has the option to 'boost' its dynamic range by one or two stops (marked as 200 or 400%). Previous Fuji 'expanded DR' cameras used a special dual-photosite Super CCD 'SR' sensor, but the S100FS does things a little differently. It would appear that - put simply - the S100FS is under-exposing the shot by one or two stops (to preserve the highlights) and applying a custom tone curve pull the other brightness levels back to their correct values.

Another way of looking at this is to think of the highlights as being shot at ISO 100 and the shadows at ISO 200 or ISO 400 since the camera is effectively applying a non-linear gain to the raw output (which inevitably looks very dark if opened in a non-Fuji development application). In effect this isn't that different to the options offered by Nikon (D-Lighting), Canon (HTP) or Sony (DRO), though Fuji has taken it a lot further by reducing the exposure so much, indicating a fairly confident view of the camera's sensitivity and noise control.

You don't get something for nothing, of course. Shooting at 400% limits you to at least ISO 400 (hence giving an exposure two stops shorter than the camera's base ISO setting), and this does mean the shadows get noisier, though to be fair the results aren't bad at all. If you can live with the additional noise, then it's a useful feature.

A little more of the shadow detail is clipped off because of additional noise, but essentially, DRange's main effect is to give almost exactly two stops of extra range in the highlights. And it does exactly as promised. In the real world the effect is most noticeable in reflective surfaces (the transition to white is much smoother, rather than just clipping), and in skies, where you are more likely to retain detail in clouds. The downside is that the images become increasingly noisy, particularly in the dark areas, but the S100FS's ISO 400 performance is good enough to make the compromise one worth accepting.

Real world examples

DRng - 100%, ISO 100 DRng - 400%, ISO 400

You can also shoot extended dynamic range images in RAW, but third-party converters won't understand that the image has been intentionally under-exposed and will produce a very dark image. You need to play extensively with tone curves, highlight recovery and fill light (or equivalent), to get the correct results from third-party software. Once you've established these correction settings, you should be able to apply them to all extended dynamic range images, though.

DRng - 400%, FinePix Studio DRng - 400%, Adobe Camera Raw

A version of this image, with corrections applied in Adobe Camera Raw, is in the samples gallery at the end of the review.



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