Nikon D300 User Manual page 419

The only useful reason I can see for doing so is when you are
using Nikon Camera Control Pro software to send pictures
directly to your computer (that software is not included with
the camera).
Here are the two settings:
▪ LOCK – Release locked – If you choose this default
setting, your camera will refuse to release the shutter
when there is no memory card present.
▪ OK – Enable release – Use this setting if you want to
use the optional Camera Control Pro 2 software to send
images from the camera directly to the computer.
Here are the screens and steps used to configure
card? (see Figure
Figure 4-81. No memory card?
1. Select f Controls
scroll to the right (see
2. Highlight
Figure 4-81, image 2).
3. Choose one of the two selections from the list. In
Figure 4-81, image 3,
4. Press the
4-81):
from the
Figure
No memory card?
Release locked
OK button to lock in the setting.
Custom Setting Menu
4-81, image 1).
and scroll to the right (see
has been selected.
419
No memory
and