Your lens isn't long enough
There isn't enough light
Your subject will remain motionless while you focus, meter and compose, but will flee 1/2 second before you press the shutter button
your lens isn't long enough
Nikon D2X, D-100, F, F2
too many Nikkor lenses
Hasselblad 500C/M
Hasselblad 500 EL/M
Pentax 6X7
