45
Light metering and exposure control
Two primary factors have to be considered when making exposure control choice, namely, meter-
ing method and exposure method:
Metering method
determines in which manner the light measurement is made and how much
of the image is taken into account( Average, Centre Weighted and Spot).
Exposure method
involves the parameters and deciding factors about how the light measure-
ment is translated into aperture and shutter speeds. Here the choice is about the camera controls
and their effect on the result or suitability for the subject. Included in this choice is the type of auto-
mation too (Manual for 100% user control, Aperture priority, Program, etc for automated control).
Some methods and modes are much more suited to various situations and applications than oth-
ers, while some depend to a greater degree on personal preference and ways of working. A discus-
sion of the points to consider in this context is beyond the scope of this manual. If you are not sure
about choice, please check in other general photographic literature for a fuller explanation. Also
check our website occasionally – www.hasselblad.com – for articles and discussions concerning
such matters.
Remember that exposure configurations are only applicable to the speed of the film in use. Ensure
you have the correct setting on the film magazine!
Since the light measuring system is TTL, filter factors, lens extension / extension ring factors, etc,
are automatically taken into account for average purposes. However, some combinations of meth-
ods and equipment can cause slight discrepancies for various reasons and therefore for critical
work you should make alternative exposures to suit personal preference.
Exposures are displayed on the grip LCD to within 1, 1/2 and 1/3 EV tolerances (dependent
on setting). This means that ‘half-stops’ are shown in a form that can differ from more
traditional displays. For example, the position between f/ 8 and f/11 is displayed as f9.5
and likewise the position between 1/30s and 1/60s is displayed as 45. Therefore a display
showing ‘f 9.5 45’ simply means ‘f/9.5 at 1/45 second’. The appearance of an ‘s’ after the
shutter speed signifies whole seconds so, for example, ‘45s’ on the display signifies an
exposure time of 45 seconds, not 1/45.
Metering method
There are three metering methods available. All three are reflective methods (measuring the light
reflected off various selected parts of the subject according to method) and are through the lens
(TTL). These have the following designations (with their respective LCD symbols):
— Average
— Centre weighted
— Spot
Average:
Commonly used for ‘average’ light situations where there is no particular dominance
of light or dark areas across the tonal range. Takes into account approximately 70% of the image
seen in the viewfinder.
Centre weighted:
Emphasises the central section of the focusing screen equivalent to approxi-
mately 20% of the image. This provides a balanced assessment and is a typical choice where the
main subject is in the centre of the image.
Spot:
The sensitive area is equivalent to approximately 2% of the image area (the central spot on
the viewfinder screen). Any parts of the image outside of this area will not affect the exposure read-
ing. This provides a very accurate measurement of specific tones.Typically used in the zone system
and similar light measuring situations where maximum control is required. Also excellent for tonal
comparison measurements. The spot mode can display ‘zones’ instead of EVs in the viewfinder
LCD( see Camera Options).
Average
(45 x 37 mm) ≈ 70%
Centre weighted
(23 x 20 mm) ≈ 20%
Spot
(diameter 7.5mm) ≈ 2%
