Fujifilm X100S Dynamic Range (JPEG)
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 camera's clipped white point down to black (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' (defined as 50% luminance) 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 above middle gray the camera can capture before it clips to white. Shadow range is more complicated; in our test the line on the graph stops 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.
The X100S's default tone curve is very similar to the X-E1 and X-Pro1's, and in fact it's virtually identical from dark midtones up to highlights, offering the same highlight dynamic range as its X-Trans cousins. Our tests show that the X100S clips to black more suddenly than previous X-Trans cameras though, giving about two stops less dynamic range in the shadows. This isn't quite what it looks like though - Fujifilm has confirmed that it made minor tweaks to the X100S's tone curve compared to previous cameras, to give a slight contrast boost in light-ish shadow areas. The more contrasty shadow response comes at the expense of dynamic range, but both shadow and highlight tone can be tweaked for more or less contrast in these areas, which allows you to get things just the way you want them, in JPEG mode.
Compared to its peers, the X100S offers a more or less equivalent dynamic range in the highlights (where, arguably, it matters most).
The X-100's color Film Simulation modes show subtly different tone curves, which translate into visible real-world differences. Velvia/Vivid is very contrasty indeed, clipping more abruptly to both white and black, while Astia/Soft echoes Provia/Standard across the highlight range but is more contrasty below middle gray, resulting in somewhat deeper shadows. The Pro Neg Hi mode lies somewhere between Velvia and Astia in terms of its shadow contrast, while Pro Neg Std closely matches Provia/Standard. Likewise, the various Monochrome modes all match Standard exactly.
Like the X-Pro1 and X-E1 the X100S has two dynamic range expansion settings to bolster its highlight range: DR200 (200%) adds an extra stop of information in the highlights, and DR400 (400%) adds two stops. Technically, the camera achieves this by applying less amplification to the sensor's output than usual prior to AD conversion to avoid clipping highlight data, then pulling-up the midtones to the correct brightness in JPEG processing. This is essentially the same process as Canon and Pentax use for their highlight-expansion modes.
An alternative way of thinking about this is that DR200 is like underexposing a stop to retain highlights then adjusting the brightness afterwards, and DR400 is like underexposing by two stops and adjusting further. Because of this, the minimum ISO available in each mode is limited: ISO 400 at DR200, and ISO 800 at DR400. The flipside to this approach is shown by ISO 100, which is effectively the opposite; i.e. ISO200 overexposed by a stop then pulled-down in processing. This results in the loss of stop of highlight range - to all intents and purposes it counts as DR50, and should therefore normally be avoided. (Note ISO 100 is only available in JPEG anyway).
In this comparison we can see the impact the DR setting has on highlight range. DR200 offers a huge 4.7 stops of highlight range, and DR400 goes another stop beyond this, disappearing off the scale of our graph. Note that this advantage isn't just for JPEG shooters - it extends to Raw files too. On paper at least this is very impressive indeed; we'll see how it translates into real-world results in the final review. The Fujifilm X100S also comes with the same Shadow and Highlight Control functions as the X-Pro1. You can read more about this feature on the dynamic range page of our X-Pro1 review.