As the graph above shows, at low sensitivities the dynamic range of the two cameras is remarkably similar, although the Nikon Df has around a 0.7EV better dynamic range at its peak. However, as the ISO sensitivity increases, the smaller sensor of the Fujifilm X-T1 has an advantage, and in fact that there is little difference in the dynamic range between ISO 100 and ISO 1600. There are some very slight peaks in the graph of the X-T1, but these are within a margin of error and don’t interfere
with the overall trend.

The original raw images below were shot at ISO 200, and then both images have had their exposure increased by +5EV in Adobe Camera Raw 8.4. The detail that becomes visible is quite astounding and there is little to choose between each model. At a push, I would say that, at this sensitivity, the Df just edges the X-T1 in showing slightly more fine detail, but generally at low sensitivities both cameras are a match for each other.

Image: The image was deliberately underexposed and then brightened by +5EV. The enlargements show what detail can be recovered