Mamiya 7 II Instructions Manual page 23

Illuminating "LT" indicates that the shutter is set for a relatively long exposure from between 1 to 4
seconds.
When taking pictures at such slow speeds you must be able to hold the camera very steady, or increase
aperture to obtain higher shutter speeds, or best of all, use a sturdy tripod.
Under AE (automatic exposure) or AEL (AE lock), the LED display in the viewfinder will continue to
operate as long as the shutter release button is touched slightly. When you take your finger off the
button, the LEDs will go out.
When "M" LED blinks, it indicates overexposure.
Rotate the aperture ring to stop down to a
smaller f/stop until an LED indicates proper
exposure.
Blinking "LT" indicates under-exposure: rotate
the aperture ring until the LED stops blinking to
increase exposure.
21
Taking Photographs