True Exposure Explained - Hasselblad H6D User Manual

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5.5

TRUE EXPOSURE EXPLAINED

Light level at image plane
True Exposure is an HC/HCD lens function that allows the
shutter speed to remain unaffected when stopping down. This
effect is perhaps not so commonly understood as it is restricted
specifically to integral lens shutters as opposed to focal plane
shutters.
When a lens is stopped down, the effective shutter speed
becomes longer, consequently affecting the set exposure.
At slow shutter speeds the effect is minimal but at faster
speeds, 1/500s, the effect becomes clearly visible. Automatic
compensatory measures in speed setting adjustments are
employed.
As compensation can only be put into effect where speeds
can be adjusted, this prevents the possibility of adjusting
the fastest speed of 1/800s or 1/1000, depending on lens
H6D
T fully open
T stopped down = T Fully open
(using True Exposure)
T stopped down > T Fully open
(without True Exposure)
Maximum aperture
Stopped down one stop with True Exposure ON
Stopped down one stop with True Exposure OFF
type. To counter this, compensatory adjustments are therefore
made to the aperture instead to retain the set exposure. This
compensation is not always required and when using flash
or strobe as the main light source it is actually undesirable
because compensation will result in underexposure. Therefore,
when using flash/strobe as the main light source, you should
set True Exposure to OFF in Main Menu > Camera Settings >
Exposure > True Exposure in the Camera Sensor Unit Display.
You can download a complete explanation of this situation from
www.hasselblad.com.
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