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H4D
Trueexposure
True Exposure is an HC/HCD lens function that allows the shutter speed to remain un-
affected 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, e.g. 1/500s, the effect becomes clearly visible. As Hasselblad knows exactly how
the shutters behave in HC lenses, automatic compensatory measures in speed setting
adjustments are therefore employed.
As compensation can only be put into effect where speeds can be adjusted, this pre-
vents the possibility of adjusting the fastest speed of 1/800s. To counter this, compensa-
tory adjustments are therefore made to the aperture instead to retain the set exposure.
However, this compensation is not always required and when using flash/strobe as the
main light source it is actually undesirable because compensation will result in underex-
posure. Therefore, when using flash/strobe as the main light source, you should set True
Exposure to OFF in Custom Options #13.
Note
You can download a fuller ex-
planation of this situation from
www. hasselblad.com.
True exposure
Light level at
image plane
T fully open
T stopped down = T fully open
(using True Exposure)
T stopped down > T fully open
(without True Exposure)
Time
Maximum aperture
Stopped down one stop with True Exposure mode ON
Stopped down one stop with True Exposure mode OFF
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