Table of Contents
Advertisement
Centre Weighted
(23 x 20 mm) ≈ 25%
CentreSpot
(23 x 20 mm) ≈ 25%
Spot
(diameter 7.5mm) ≈ 2.5%
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( Centre Weighted, CentreSpot and Spot).
Exposure method involves the parameters and deciding factors about how the light meas-
urement is translated into aperture and shutter speeds. Here the choice is about the camera con-
trols and their effect on the result or suitability for the subject. Included in this choice is the type
of automation 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 all exposure configurations are only applicable to the ISO setting in use!
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
methods and equipment can cause slight discrepancies for various reasons and therefore for criti-
cal 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 (depend-
ent 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):
— Centre Weighted
— CentreSpot
— Spot
Centre Weighted: 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 25% of
the image seen in the viewfinder.
CentreSpot: Emphasises the central section of the focusing screen equivalent to approximately
25% 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 2.5% 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
reading. 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 excel-
lent for tonal comparison measurements. The spot mode can display 'zones' instead of EVs in the
viewfinder LCD (see Camera Options).
76
Advertisement
Table of Contents
