Nikon D750 User Manual page 528

When used with the AF-S NIKKOR 14–24mm f/2.8G ED, the flash
will be unable to light the entire subject at all ranges.
The built-in flash can also be used with the following non-CPU
lenses: Nikon Series E and 24–300 mm NIKKOR (AI-S, AI-, and AI-
modifed). AI 50–300mm f/4.5, modified AI 50–300mm f/4.5, AI-S
50–300mm f/4.5 ED, and AI 50–300mm f/4.5 ED lenses must be
used at a zoom position of 70 mm or above. With AI-S and
AI 25–50mm f/4 ED lenses, the ranges above which vignetting
will not occur are: 2.0 m (6 ft 7 in.) at a zoom position of 25 mm
and 1.0 m (3 ft 3 in.) at a zoom position of 28 mm; vignetting will
not occur at zoom positions of 35 mm or above.
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