Nikon D3300 - Manual (Page 374)

354 Technical Notes
A Using the Built-in Flash
When using the built-in flash, be sure the subject is at a range of at
least 0.6 m (2 ft) and remove lens hoods to prevent vignetting
(shadows created where the end of the lens obscures the built-in
flash).
Shadow Shadow
Camera Minimum distance without vignetting
D7100/D7000/D5300/D5200/D5100/D5000/
D3300/D3200/D3100/D3000/D300 series/
D200/D100/D90/D80/D70 series/D60/D50/
D40 series
No vignetting at any focus distance
Because the built-in flash units for the D100 and D70 can only cover
the angle of view of a lens with a focal of 20 mm or more; vignetting
will occur at a focal length of 18 mm.