6
7
6
7
ISO 100
Bright daylight, sunny conditions, hand-held
shooting where clean images are a priority.
ISO 200
Where faster shutter speeds are required or
slightly longer lenses, or where you need
extra fl exibility with apertures/shutter speeds.
ISO 400
For indoor or overcast conditions; or if you
want to avoid using fl ash, or need a fast
shutter speed/aperture to shoot hand-held.
ISO 800
For overcast or dark indoor shooting, sports
or action photography where you need to
freeze the motion and some noise is okay.
ISO 1600
Night time, low-light shooting, very long lens
shooting; noise will almost certainly become
quite noticeable in the shot.
ISO 3200
For hand-held night time or low-light
shooting or where high shutter speeds are
required. Noise will be very evident in shots.
HIGH ISO
LOW ISO
Above: One stop over
METERING, SENSITIVITY
AND WHITE BALANCE
Metering, sensitivity and white balance are three key aspects of the way your image
looks once you press the shutter button, irrespective of the focus, sharpness or
number of pixels you throw at it. Here we will look at key components of the DSLR
that make an image look right in terms of colour, image noise and exposure
Sensitivity
A camera’s ISO setting defi nes its sensitivity
to light. The higher the ISO, the more
sensitive it becomes and vice versa. But
a downside of higher sensitivities is the
introduction of image noise (analogous to
grain in fi lm) that can adversely affect a shot.
Think of noise as interference, just like the
‘snow’ in a badly tuned TV picture. It appears
because increasing sensitivity is actually
turning up the gain on the sensor. Things that
can affect noise include internal electrical
interference from camera components, heat
and the amount of light. The light is the good
signal, everything else is noise, and hence a
good signal to noise ratio is important: the
more light the less noise. This is why noise
becomes more evident in low-light shots.
To reduce the effects of noise within your
images, try to use the lowest possible setting
for the shot at hand. Set it to ISO 100 or its
lowest setting for best overall results. Set
your camera’s noise reduction (it’ll be there
in the set-up menus) to ‘On’ when shooting
above ISO 400. Bear in mind however, the
extra image processing required might slow
the speed at which the camera can handle
the images and may affect detail in the
shots, since it tries to ‘smooth’ away the tiny
speckles of blue, red or grey that denote
noise in a digital image.
Here is a ready reckoner for the use of a
particular ISO (sensitivity) and why, based
upon typical DSLR sensitivity settings...
Metering
DSLRs come with a light-measuring system
or ‘metering’ to ensure your shots are
properly exposed; not too light, and not too
dark, for example. The system is designed
to measure light refl ected from your subject
from either the entire frame (Matrix or Evalu-
ative metering) a central-biased average
of the scene (Centre Weighted), or from a
small spot, usually in the middle of the frame
(Spot metering). You can set the camera to
use whatever metering method you require
to achieve a well-balanced exposure for the
task, but its effect can be altered to suit the
subject (or your preference) by controlling the
aperture and shutter speeds in the manual
modes, for example.
Importantly, many DSLRs have their
focusing zones linked directly to the metering
system, thus providing a very accurate
bias in the metering to whichever AF point
(or points) are in use. This makes accurate
metering from specifi c (often tiny) areas in
a scene possible and provides a great level
of extra control should it be required, if, say,
the camera’s main metering systems are not
cutting the mustard.
White balance
Your DSLR offers a variety of White Balance (WB)
or colour temperature settings to combat colour
casts from differing light sources. Whether in
menus or accessed via an external control it is
not always a good idea to leave your camera set
to its ‘Auto WB’ setting. The colours may not be
rendered as accurately in a shot as needed. To
help get the most from any shot, use the correct
WB setting for the job at hand: daylight setting for
daylight and so on. Moreover, if you are not sure,
use the custom setting; DSLRs enable you to tailor
the WB quickly and simply to any lighting type.
The typical settings available will include all or
some of those set out in the box below, indicated
using small icons, text or both. Some DSLRs have
a Kelvin scale for even fi ner tuning as well as the
custom mode. The latter allows you to set WB
specifi cally for the current ambient light; typically
this involves taking a shot (in the custom WB set-
up screen) of something plain, fi lling the frame and
you know to be white: paper, anything. It does not
even have to be in focus. Using the custom method
of WB control means no matter what the ambient
light, you will always have white whites!
Typical auto white balance settings
•
Auto:
General scenes/mixed lighting but colours may not
be accurate in some lighting.
•
Direct Sunlight:
Ideal for bright, sunlit daylight.
•
Shade:
Best for shade or shots in deeper shadow.
•
Cloud:
Use for overcast daylight shots.
•
Flash:
Use with fl ash photos including fi ll-in fl ash.
•
Incandescent:
Use for atmospheric candlelit images.
•
Fluorescent:
Use when shooting photos using light from
kitchen- style strip lights.
•
Tungsten:
Ideal for household bulb/lamplight shots and
shots taken indoors.
•
Custom:
User set (see text above) to whatever ambient light
is present in any conditions for most accurate colour rendition.
Here is a quick guide to colour temperature using the Kelvin scale
and the corresponding (typical) light source. The lower the Kelvin
fi gure, the warmer (or redder) the colour is going to be. The higher
the Kelvin fi gure, the hotter the light source is and bluer the colour.
1,700-1,800k
= Match fl ame
2,000-3,000k
= Sun: sunrise and sunset
2,500-2,900k
= Household tungsten bulbs
3,200-7,500k
= Fluorescent lights
5,000-5,400k
= Sun: direct sun at noon
5,500-6,500k
= Daylight (bright sun in clear sky)
6,000-7,500k
= Overcast (cloudy) sky
7,000-8,000k
= Outdoor shade
MATRIX OR EVALUATIVE
These are many small (in some cases over
200) metering ‘zones’ around the frame that
are used to intelligently assess and measure
light from all locations within the frame (based
on pre-programmed algorithms) to get a
balanced exposure. This mode is ideal for
general photography or broader subjects
such as landscapes or subjects where there
are no tricky high-contrast areas.
CENTRE WEIGHTED
A central portion of the frame (the size of this
zone can be adjusted on some DSLRs) is
‘weighted’ to simply measure the average of
light non-judgmentally, without trying to apply
any adjustments. Ideal for where you want
to bias the exposure to the central area, in
backlit subjects for example. It’s also useful
in that you can predict how it will react to a
scene and when it will be fooled, so you can
more easily compensate for it.
SPOT
A very small area of the frame (1%-8% of the
frame, depending on the camera) that is ideal
for measuring light from a very specifi c area
in a scene. Ideal for macro (close-up) work,
or for portraits (metering from a skin tone) or
for high-contrast scenes, so you can exclude
bright highlights/deep shadows (or meter
from both and apply an average).
