Nikon D750 User Manual page 422

Retouching Copies
D
Most options can be applied to copies created using other retouch
options, although with the exceptions of Image overlay and Edit
movie > Choose start/end point each option can be applied only
once (note that multiple edits may result in loss of detail). Options that
can not be applied to the current image can not be selected.
A Image Quality
Except in the case of copies created with Trim, Image overlay, NEF
(RAW) processing, and Resize, copies created from JPEG images are
the same size and quality as the original, while copies created from NEF
(RAW) photos are saved as large fine-quality JPEG images. Size-priority
compression is used when copies are saved in JPEG format.
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