Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 100, ƒ/1.4, 1/30
I shot the chart for those pixel peepers. I was shooting some photos side by side comparison of the D4 to the D5 at different ISOs.
I did a custom white balance using the ExpoDisc.
Click on the images to see their full resolution .
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 100, ƒ/1.4, 1/30
Now ISO 400
Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 400, ƒ/1.4, 1/125
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 400, ƒ/1.4, 1/125
Now ISO 1600
Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 1600, ƒ/1.4, 1/500
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 1600, ƒ/1.4, 1/500
Now ISO 5600
Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 5600, ƒ/1.4, 1/2000
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 5600, ƒ/1.4, 1/2000
ISO 12800
Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 12800, ƒ/1.4, 1/4000
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 12800, ƒ/1.4, 1/4000
ISO 25600
Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 25600, ƒ/1.4, 1/8000
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 25600, ƒ/1.4, 1/8000
ISO 51200
Nikon D4, Sigma 35mm ƒ/1.4 DG Art, ISO 51200, ƒ/5.6, 1/1000
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 51200, ƒ/5.6, 1/1000
ISO 102400
Nikon D5, Sigma 35mm ƒ/1.4 DG Art, ISO 102400, ƒ/5.6, 1/2000
My opinion is that the D5 is giving you between 2 to 3 stops higher ISO with similar noise as the D4 at those lower ISO numbers. I would say that the D5 25600 is about the equivalent of the D4 ISO 6400. However, you can make that call yourself from the photos above.