Nikon D750 User Manual page 264

The camera can store data for up to nine non-CPU lenses. To
enter or edit data for a non-CPU lens:
1
Select Non-CPU lens data.
Highlight Non-CPU lens data in the
setup menu and press 2.
2
Choose a lens number.
Highlight Lens number and press 4
or 2 to choose a lens number.
3
Enter the focal length and aperture.
Highlight Focal length (mm) or
Maximum aperture and press 4 or
2 to edit the highlighted item.
4
Save settings and exit.
Press J. The specified focal length and aperture will be
stored under the chosen lens number.
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