Comparing the APS-C sensor from the Fuji X-T1 versus the full frame Nikon DF may seem like a losing battle. A camera twice as heavy and expensive should beat the X-T1 in all sections except in portability and the damage to the pocketbook. However, the editor of the blog Soundimageplus David Taylor-Hugues has not hesitated to compare both cameras in a of high ISO battle.
Nikon DF vs Fuji X-T1: ISO 3200
Nikon DF vs Fuji X-T1: ISO 6400
Above is one of the clips detailing 100% of the comparison, a total of three: A ISO 3200, ISO 6400 and ISO 25600, JPEGs direct from the camera. With the Nikon DF they used a Nikon AF-S 24-85mm, 3.5-4G ED VR versus a Fujinon XF 18-55mm f / 2.8-4 R LM OIS from the Fuji X-T1. Both lenses had a fixed aperture set to f/4. You can see the rest of the examples on the Soundimageplus webpage.
Nikon DF vs Fuji X-T1: ISO 25600
The author of the test is clear: the Nikon DF has more detail in each of the examples but the excellent results of the X-T1 are surprising. To the extent that they claim to be "the best high quality ISO images" he has seen in a APS-C format camera.
Even then, they note the different "interpretation" of the ISO values of Fuji vs. Nikon: approximately half past exposure for the latter something that can quite distort some tests if not taken into account.
In conclusion, consider the Fuji X-T1 can be used perfectly for as a "workhorse" professional for any task. In his opinion, you would have to look very carefully to "see significant differences" in prints images at high ISO from Nikon DF and Fuji X DF-T1.