Raw Dynamic Range

Exposure Latitude

In this test we look to see how tolerant of pushing exposure the X-T10's Raw files are. We've done this by exposing our scene with increasingly lower exposures, then pushed them back to the correct brightness using Adobe Camera Raw. Examining what happens in the shadows allows you to assess the exposure latitude (essentially the dynamic range) of the Raw files.

Because the changes in noise are primarily caused by shot noise and this is mainly determined by the amount of light the camera has had access to, the results are only directly comparable between cameras of the same sensor size. However, this will also be the case in real-world shooting if you're limited by what shutter speed you can keep stead, so this test gives you an idea of the amount of processing latitude different formats give.

The X-T10 uses a Fujifilm's X-Trans color filter pattern on its sensors but there's every reason to suspect the silicon behind it is otherwise the same on Bayer CMOS chips. The X-T10's results are certainly consistent with rival APS-C chips in terms of how little noise they add to the image they capture. Compared here with the Nikon D5500 you can see very similar noise levels when the images have been shot at the same aperture and shutter speeds (and hence would show similar amounts of shot noise).

This gives plenty of flexibility, when it comes to pulling extra dynamic range out of the shadows: something you can't always take for granted, even on cameras with more modern sensors. It even allows more confidence for pushing than the likes of the Sony a6000, which is one of its most capable peers.

ISO Invariance

A camera with a very low noise floor is able to capture a large amount of dynamic range, since it will add very little noise to the detail captured in the shadow regions of the image. This has an interesting implication: it minimises the need to amplify the sensor's signal in order to keep it above that noise floor (which is what ISO amplification conventionally does). This provides an alternate way of working in situations that would traditionally demand higher ISO settings.

Here we've done something that may seem counter-intuitive: we've used the same aperture and shutter speed at different ISO settings to see how much difference there is between shooting at a particular ISO setting (and using hardware amplification) and digitally correcting the brightness, later. This has the advantage that all the shots should exhibit the same shot noise and any differences must have been contributed by the camera's circuitry.

As you can see, there's essentially no difference between shooting at a high ISO and using a lower ISO and pushing the file later. This not only suggests the sensor is adding very little downstream read noise, it also opens up the option to use the shutter speed and aperture value you'd usually use for a high ISO shot, while staying at a low ISO to use a much lower level of amplification. Using this lower level of amplification means that highlight detail is less likely to get over-amplified and blown-out.

Interestingly, the camera's DR modes exploit this behavior: they give you the choice of using one of three different exposures, while still maintaining a minimal level of hardware amplification. But, unlike most cameras, it then offers matching tone curves to give usable JPEGs (rather than this being a Raw-only technique).

The DR100% mode is comparable to the way any other camera treats ISO. But when you switch to DR200%, the camera halves the exposure (which you'll see as a jump in the lowest available ISO setting), but leaves amplification the same, meaning that you capture an extra stop of highlight information, which is then incorporated into the JPEG using a flatter tone curve. DR400% does this again: another 1EV drop in exposure without a change in amplification, to protect an extra stop of highlight information.

Take three shots at ISO 800, one at DR100%, one at DR200% and one at DR400% and you'll see the results. They'll have the same noise level, because almost all of the noise is coming from shot noise, which is defined by exposure, but the DR400% mode will have more highlight detail.