Nikon D300 User Manual page 216

greatly magnified with a long lens, and a Minimum shutter
speed of 1/250s to 1/500s or more may be required (max is
1/4000s).
ISO Sensitivity Auto Control from the
Camera's Perspective
For fun, let's listen to the camera talk to itself while you take
pictures in low light with ISO sensitivity auto control enabled.
As we listen in on the D300(S) thinking—in the next
paragraph—we need to know that the current Maximum
sensitivity setting is ISO 400, and the Minimum shutter speed
setting is 1/30s (as shown in Figure 3-52):
Nikon D300(S) thinking: "Okay, Auto ISO is on! The light
is dropping and my current i/60s shutter speed at ISO 200
sensitivity won't let me make a good exposure. I'll slow the
shutter speed to the minimum of 1/30s, as my owner specified
in my Minimum shutter speed setting. More pictures are
incoming, and the light is still dropping! I can't go any lower
on the shutter speed for now, since my owner has instructed
me
to keep the Minimum shutter speed at 1/30s unless I can't get
a good picture. I'll have to start raising the ISO sensitivity.
Here comes more pictures, and whew, it's getting dark! I've
now raised the ISO sensitivity to my Maximum sensitivity
level of ISO 400, which is as high as I am allowed to go. I
have no choice now but to go below the 1/30s Minimum
shutter speed my owner has specified. I hope I'm on a
tripod!"
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