Digital Camera magazine by misuari87

VIEWS: 86 PAGES: 48

									                                 Complete photography guide




     Master
Exposure
TAKE STUNNING PHOTOS
USING OUR EXPERT TIPS
■ How to read a histogram
■ Metering for different tones                      VITAL
■ Coping with unusual lighting                     SKILLS
                                                   GUIDE
 Master
Exposure
 Trying to get the ‘correct’ exposure is one of the
 greatest challenges for those beginning in
 photography. But it needn’t be. This book will
 show you the pitfalls to avoid, when to alter
 your camera’s settings (and by how much) and
 how to get creative with metering.




                                                Exposure   3
  Master
Exposure
TAKE STUNNING PHOTOS
 USING OUR EXPERT TIPS
  Contents
■ Exposure basics                       p10

■ Adjusting exposure                    p14

■ When things get tricky                p16

■ Master of exposure: Ansel Adams       p20

■ Background problems                   p22

■ Unusual lighting                      p26

■ Master of exposure: Galen Rowell      p30

■ How to read a histogram               p32

■ Controlling the dynamic range         p36

■ Using a neutral density grad          p38

■ Master of exposure: Pål Hermansen     p42

■ Low light exposures                   p44

■ High key/low key                      p46

■ Top 10 tips                           p49




                             Exposure     7
Use your grey matter
T     he biggest advantage digital has over film is the
      fact that you can check your shot once you’ve
taken it. You can bring up a histogram to check the
brightness range of a scene – and make sure you’re not
underexposing or overexposing it. You can, if your
camera allows, switch on a flashing highlight to show
you any blown highlights where detail will be lost in
your photograph. You can then change your exposure
accordingly. And if all that fails to produce the balanced
exposure you want, you can go some way to rectifying
it while image-editing.
   It is, however good to get things right first time – to
produce a high-quality image in-camera which you
only have to do minimal tweaking with later. This book
arms you with practical advice for getting the
exposures you want, and the confidence to take
control when the camera’s being fooled. We’ve got
clear examples of when this can happen and what you
should do. We also show you the inspiring work of
three master photographers to give you an idea of you
what can be achieved once you’ve nailed the basics –
which start on page 10…




Marcus Hawkins
Editor, Digital Camera Magazine




8                 Exposure
Exposure
basics
O       n the face of it, exposure seems a pretty
        straightforward business. In order to
produce a good range of tones in your picture,
the camera has to make sure the right amount
of light reaches the sensor. And it does this (or
you do) by adjusting the length of the exposure
(the shutter speed) and the light intensity (the
lens aperture). The image is formed by the
accumulation of light on the sensor during the
exposure. All digital cameras incorporate
exposure systems which will do this
automatically, so what’s the problem? Even the
most sophisticated metering system is unable
to understand what the camera’s looking at, or
what the photographer’s intentions might be.
This is where you need to take control.




10                 Exposure
      Digital’s dynamic range                             Mid-tones
      Cameras will struggle to deal with scenes where     The idea of ‘mid-tones’ is important in exposure.
      there’s an extreme brightness range. With film,      On one level, it describes areas of the scene
      this is called ‘exposure latitude’, with digital    which are more or less in the middle of the tonal
      cameras it’s called ‘dynamic’ range. On a very      range. You might say these are the parts you
      bright sunny day, it may be impossible to find an    want to expose correctly. But how dark or light
      exposure which records some detail in the           are these mid-tones? In order to work out the
      shadows without ‘blowing out’ the highlights, or    exposure, your camera has to work to a
      vice versa. It’s generally agreed that digital      standardised average ‘grey’ tone – 18% grey, to
      cameras have a similar exposure latitude to slide   be precise – and try to adjust the exposure to
      film, and you can start off by assuming a            reproduce your subject with this level of
      dynamic range of about 4 EV values. This means      brightness. This is one of the principle drawbacks
      you should still be able to see or recover useful   of all built-in camera meters, no matter how
      shadow detail 2 EV darker than the mid-tones        sophisticated. They don’t know what it is they’re
      in your image, and highlights 2 EV brighter than    looking at, and what intrinsic tone the subject
      this mid-tone value should record well too. So      ought to have. All subjects will be reproduced to
      what do you do if the brightness range in the       this 18% grey value, which is a problem we’ll
      scene exceeds this 4 EV range? There are ways       come on to shortly.
      of dealing with this, and we look at these a
      little later on.




       At first glance, this scene seems to average
       out an overall mid-tone. However, the
bright wall of the cottage is overexposed. Dialling
in some underexposure would take the edge off
this, at the expense of detail in the shadows.


                                                                               Exposure                   11
Metering patterns                                    Aperture and shutter speed
Light meters may not be able to understand that      Digital cameras control exposure using both
different subjects may have different intrinsic      shutter speed and aperture. Why both? Wouldn’t
brightness levels, but camera makers have at least   one or the other do the job? There are creative
been able to allow for difficult and contrasty        advantages to these two means of exposure
lighting conditions. By default, digital cameras     control. Smaller lens apertures offer more depth
use ‘multi-pattern’ metering systems that            of field (near-to-far sharpness), while fast shutter
measure the light values at numerous points in       speeds let you freeze fast-moving objects.
the scene. This helps them build up a picture of     Shutter speed and aperture are interchangeable,
the type of lighting you’re shooting in, and the     so that if you want to use a smaller lens aperture,
camera may adapt automatically to backlighting,      you can compensate with a longer exposure. Or,
for example. Multi-pattern metering systems are      if you want a shorter exposure, you simply set a
hard to second-guess, though, and many               wider lens aperture. For example, if your camera
photographers prefer simpler ‘centre-weighted’       indicates an exposure of 1/250sec at f/8 but you
metering, which averages the whole scene but         want to shoot at 1/1000sec, which is two stops,
places extra emphasis on the central area. Spot      or EV values, faster, you need to increase the
metering is very specialised. It takes a reading     aperture value by two stops as well, to f/4. Some
from a very small area of the scene only.            cameras allow you to adjust shutter speed and
                                                     aperture values in 0.3 EV steps, but the same
                                                     principle applies – a change in one must be
                                                     mirrored with a same-sized change in the other.



                                                              To blur the crashing waves in
                                                         this scene, a smaller lens aperture
                                                             has been selected in order to obtain
                                                                            a slow shutter speed.




                                                          When faced by a mid-tone scene
                                                          such as this, multi-pattern metering
                                                     systems can be trusted to produce well-
                                                     exposed photographs.



12                 Exposure
Exposure   13
Adjusting                                            +1.5 EV



exposure
S   o how precise do you have to be with
    exposure? Even though digital cameras only
have a certain amount of ‘exposure latitude’, in
practice there are many different ways of
interpreting a scene, and many exposure errors
can be rectified or at least improved with a bit of
image-editing. To give you an idea of how the
subject brightness changes with exposure, here’s
the same scene at seven different exposure
values, all shot at the same lens aperture, but
with shutter speeds 0.5 EV apart. These also
demonstrate the idea of exposure latitude and
dynamic range. There isn’t one shot where
detail’s been recorded both in the foreground
and the garden outside – the scene is outside the
dynamic range of the camera’s sensor. You might
prefer the ‘overexposed’ shot because it shows
the subject’s face with a nice high-key effect, or
a darker silhouetted version. Or you might open
one of the in-between shots in Photoshop and
attempt to balance the tones more evenly.




The shot with the biggest increase in
  exposure works well – it ‘bleaches
 out’ a potentially distracting background.


14                 Exposure
+1 EV     +0.5 EV    0 EV




-0.5 EV    -1 EV    -1.5 EV

                         Exposure   15
When things
get tricky
                                            Metering for dark tones/black
W          e explained in the previous
           section that camera exposure
systems could adapt to a degree to
                                            We used a black background for this shot
                                            of an ornamental elephant, which itself
                                                                                              No Adjustment

‘difficult’ lighting, but that they had no   was a mixture of dark red and black. The
sense of the intrinsic lightness or         camera didn’t know any of this, of course.
darkness of specific subjects. But does      All it could do was measure the amount of
this really make much difference? Indeed    light it ‘saw’. Not surprisingly, this wasn’t
it does. If any of your digital camera      very much! As a result, the camera
shots come out badly exposed, it’s often    increased the exposure. Remember, all it
the intrinsic brightness of the subject     can do is attempt to render the subject as
that’s caused the problem, not ‘difficult’   an overall 18% grey tone, because while
lighting or any error on your part.         you and I might realise the elephant and
Just to show you how much                   the background is black, the camera
difference intrinsic subject brightness     doesn’t have the cognitive powers of the
does make, we’ve arranged a series of       human brain. It’s dark, increase the
still-life experiments…                     exposure. That’s the limit of its thinking.
                                            The result isn’t too hard to predict; an
                                            18% grey elephant against an 18%
                                            grey background.




                                                                                                The black background and dark subject
                                                                                                fooled our camera’s meter. Left to its
                                                                                            own devices, it overexposed by 2 EV.




16                 Exposure
-2 EV




        Watch out for highlights
        Our elephant shot reveals something else
        that’s interesting, too. In the overexposed
        version, look at the dried flowers in the
        foreground. They’re actually close to an
        average 18% grey tone in real life, but
        because the camera’s increased the
        exposure, they’ve been almost completely
        burned out. However, by manually
        overriding the exposure and reducing it by
        2 EV, we’ve not only restored the elephant
        and the background to a ‘proper’ black,
        we’ve restored the correct tones to the
        dried flowers. The same will apply if you’re
        photographing black birds with bright
        beaks, for example. When you’re
        photographing dark-toned subjects, the
        camera will often increase the exposure
        and lose highlight detail in other parts of
        the scene. The subject’s darkness doesn’t
        have to be as extreme as that in our
        example. If you’re shooting dark-toned
        vegetation, for example, reducing the
        exposure by 0.7 EV to 1 EV is often a good
        idea to preserve the depth of colour and
        highlight detail.




                      Exposure                  17
Metering for light tones                        fairly light-toned, along with the cloth           shot. At first you might need to experiment a
Unusually dark-toned subjects are not an        beneath them, but even so you might expect         great deal to find appropriate EV
everyday problem. Light-toned subjects are      the camera to expose them correctly without        compensation values for light or dark-toned
far more common, and they typically distort     any help. The result, though, is distinctly dull   subjects. But with practice, and a growing
the camera’s meter reading to a greater         and gloomy. Only by reshooting with                understanding of your camera’s behaviour, it
degree. Our still life shot demonstrates this   +0.3 EV compensation were we able to               gets a lot easier to work out when to override
well. The ginger, onions and squash are all     restore a realistic-looking brightness to the      the camera and how much by.


  No Adjustment                                                            +0.3 EV




  These vegetables are lighter-toned than the
  average 18% grey looked for by the camera’s
  meter, so we needed to apply EV compensation
  to make sure this is how they were reproduced.



18                 Exposure
  No Adjustment                                                                +2 EV




  If you’re photographing anything white, beware! Your
  camera’s meter will attempt to reproduce it as a muddy
  grey, so you need to intervene. This shot required +2
  EV exposure compensation to look ‘right’.


Metering for white                                  life demonstrates this very well. Remember,      default black elephant shot, demonstrating
White subjects are a special case, and the          we want objects to appear in photos as they      how the camera attempts to reduce all tones
cause of the most severe underexposure              do in real life, and not reduced to the 18%      to the same value. In order to reproduce the
problems. They’re a special case because the        grey assumed by camera meters. Our first          whiteness of our subject, we had to increase
world is full of white objects and                  attempt, shot using the camera’s default         the exposure value by 2 EV. You’ll have to do
backgrounds, and because you might be               exposure reading, was a disaster. Indeed, the    the same with snow scenes, for example, or
surprised at just how bright they are. This still   overall tones are very similar to those of the   close-ups of wedding dresses.




                                                                                                                     Exposure                  19
Master of
exposure
Ansel Adams

T    here can’t be many people who’ve never seen an
     Ansel Adams photograph. He is the acknowledged
master of landscape photography. He achieved so
much before his death in 1984 of heart failure at the
age of 82. Adams was both a photographer and
conservationist and started the f/64 group (an
association of Californian photographers who
promoted ‘pure’ photography) with Edward Weston in
1932. He’s perhaps better known for developing the
‘zone’ system for exposure, a technique which enabled
him to visualise how he would print the various parts
of the image, and expose the negative accordingly. The
tonal range he managed to extract from his black and
white film was simply incredible.




20                Exposure
                     This is unmistakably an Ansel
                     Adams landscape. The
                     richness, depth and detail is
           astounding, the exposure capturing
           every nuance of light. It pictures the
           Tetons and Snake River in Grand Teton
           National Park, Wyoming, and was shot
           in 1942.




                To learn more about Ansel
                Adams, pay a visit to
© Corbis




           anseladams.com.


                       Exposure                 21
Background problems
I  t’s not necessarily the subject of your
   photograph that can give you exposure
headaches. The tone of the background is just
                                                  judge exactly how much emphasis the camera
                                                  is giving to the subject itself, since multi-
                                                  pattern metering systems may concentrate on
                                                                                                    ginger take up nearly all of the frame, while in
                                                                                                    the other they’re quite small relative to the
                                                                                                    background. In both cases the camera’s
as important, and can have a big influence on      the object in the middle of the frame, which      default auto-exposure readings were used.
the exposure reading. Even if your subject        may or may not be where your subject is.          The close-up shot is correctly exposed, but in
consists of fairly even mid-tones, an unusually                                                     the zoomed-out version, the larger proportion
light or dark-toned background can produce        Size matters                                      of dark background has fooled the camera
exposure errors. The size of this error will      This shot uses a mid-tone subject set against a   into overexposing by 1.3 EV.
depend on how much of the frame is taken up       dark background, but shot at two different           We tried the same experiment using a light
by the background. It can also be hard to         zoom settings, so that in one the onions and      background. By zooming right in on the


                                                                                                                 You may not encounter
                                                                                                                 completely black
                                                                                                           backgrounds like this when
                                                                                                           you’re out shooting, but dark
                                                                                                           tones will have the same effect.




                                                                                                               Light backgrounds cause
                                                                                                                  mid-toned subjects to
                                                                                                             underexpose if they’re not big in
                                                                                                           the frame. Bear this in mind when
                                                                                                           framing people against pale skies.


22                 Exposure
artificial fruit, we’ve excluded nearly all of the
background, and the resulting exposure is pretty
well spot-on. When we zoomed out, though, the
proportion of the frame taken up by the
background was far higher, leading the camera to
reduce the exposure by 1.3 EV, which has left the
shot underexposed. The degree to which the
background influences exposure will depend on
the amount of the frame it takes up and its
brightness, but it can make a big difference.




                                                    Exposure   23
Complimentary tones
Here’s another experiment showing how the
exposure changes when you place a dark
subject against a light background. In this
case the best exposure is the middle one,
because the light background has reduced
the exposure. This helps render the dark
tones of the lenses more accurately.
   You can also see what happens when you
place a light subject against a dark
background. The results are similar. Close-up,
the while flowers and vase in our set-up
cause the camera to underexpose. In the
wideangle shot, the dark background has
caused overexposure. The middle shot is the
best because the tones average out well.




24                 Exposure
Exposure   25
Unusual
lighting
J  ust to make life that little bit more awkward,
   it’s often the most dramatic and ‘difficult’
lighting that makes the most exciting
photographs. You face two challenges here. The
first is that the brightness range of the lighting
will often exceed the dynamic range of your
camera’s sensor, so you have to decide which is
the most important part of the scene and base
the exposure on that, leaving extreme highlight
or shadow detail to disappear. Once you’ve done
that, you need to work out how to take an
exposure reading that will render the important
part of the scene properly.




      Backlit images can be some of the
     most exciting, but they also provide
         plenty of exposure headaches. Most
          compact digital cameras will favour
      shadowed foreground subjects, like our
        pedestrians, and this compromise has
                         worked out well here.




26                 Exposure
Backlit subjects
With backlit subjects, the light’s coming from
behind your subject and towards the camera.
This means that the side of the subject facing you
is in shadow against a bright background. It’s
unlikely that your camera will be able to record
detail in the subject and a full range of tones in
the bright background too, so you’ve got a
decision to make. You can expose the shot to get
detail in your subject, and render the background
as a brilliant, ethereal white, or go for a silhouette
effect, as you might with a dramatic sunset, for
example. In both cases, spot metering can be the
most reliable solution because multi-pattern
metering systems can behave a little
unpredictably. Some are designed to give priority
to subjects in the centre of the frame, especially
with the tonal distribution characteristic of
backlighting (the camera can detect this). You
may get a properly exposed subject when you
wanted a silhouette, and vice versa.




                      Exposure                     27
Sidelit subjects
Sidelighting is less difficult to deal with. The
overall contrast tends to be lower because you’re
not shooting into the light. However, the long
shadows cast by the light can influence the meter
in ways you don’t want. Digital cameras,
especially non-SLR models, seem to favour
shadows over highlights in a scene, so you can
often end up with an overexposed image with
‘blown’ highlights and shadow detail that’s too
light. The strong, textural quality of sidelighting,
however, relies heavily on deep shadows and
richly-coloured highlights. It’s a good idea with
sidelit subjects to at least bracket your exposures,
or take one at the default meter reading and then
another with -0.3 EV or -0.6 EV compensation.
With digital cameras, a little underexposure is a
lot easier to correct later than overexposure.
Blown highlights are lost for good, but you can
often extract an amazing amount of colour and
detail from gloomy shadows.




         If you want to capture the full
        richness of colour and textural
    quality of sidelit subjects, you may have
  to manually reduce the exposure to retain
                         those dark shadows.


28                  Exposure
Spotlit subjects
Spotlit subjects are particularly difficult to deal
with. The situation here is comparable to that we
set up when photographing subjects against a
dark background, but the contrast in tones is
going to be even higher. Left to its own devices,
the camera will attempt to compensate for the
darkness of the background, leaving your main
subject hopelessly overexposed. The solution
here is to take a spot reading from the area being
spotlit. In addition, you’ll have to make
allowances for the intrinsic brightness of your
subject, which is one of the reasons why spot
metering is quite a skill. For example, if you’re
photographing a performer on stage in a white
costume, you might need to take a spot reading
from the costume, then dial in +2 EV exposure
compensation to make sure it reproduces as
white. Landscapes spotlit by the sun breaking
through clouds are generally easier to meter for,
thanks to their more mid-toned nature.




     Spotlit subjects are one of the
     trickiest to expose for, but spot
metering can help you out. Be careful of
metering from intrinsically light or dark-
toned objects, though.


                     Exposure                   29
Master of
exposure
Galen Rowell

T    he world lost of one its greatest wilderness
     photographers on August 11th 2002, when Galen
Rowell – and his wife Barbara – died in a plane crash in
California while returning from a photo workshop in
the Arctic. He was 61. Rowell was a perfectionist when
it came to his photographs. His search for the ‘dynamic
landscape’ meant seeking out the best light and having
the confidence to control it. Such was his mastery of
exposure, he had his own branded range of graduated
neutral density filters, developed by Singh-Ray.
    Rowell started out as a car mechanic, but gradually
began to fuse his passions of mountain climbing and
photography into a successful career. In 1972 he
received his first commission from National Geographic
– to capture an ascent up Yosemite’s Half Dome
monolith. The photographs he brought back proved so
powerful that one was selected as the cover shot.
    He went on to shoot numerous stories for the
magazine and publish an impressive series of books,
including the legendary ‘Mountain Light’ – the name
he went on to use for his photography business – and
‘My Tibet’, co-written with the Dalai Lama. He
received the Ansel Adams Award in 1984, for his
contributions to the art of wilderness photography.




30                 Exposure
            While Galen Rowell rose to
            prominence with his
            staggering images of
mountains, he was a master craftsman
of landscape and wildlife photography
as well. This shot of sunflowers taken in
the eastern Sierra, California, in 2000
shows how skilled he was at reading
light. The strong backlight and delicate
form of the flowers have been captured
with perfection. The use of a graduated
filter has tamed the harshness of the
top part of the frame, making the
dynamic range of the scene more
manageable. The resulting image
takes your breath away.




   See more of Galen Rowell’s
   awe-inspiring work at
www.mountainlight.com.


            Exposure                  31
How to read
a histogram
S     o far we’ve been basing our assessments of
      exposure levels on the appearance of images
on a screen or in print. There’s a more technical
way of assessing the tonal balance of digital
images, though, and that’s using a histogram.
Many cameras can display ‘live’ histograms as
you compose a shot and/or histograms for saved
images. You can display a histogram in
Photoshop and other image-editors, too.
   The histogram will tell you whether you have
‘blown’ highlights, blocked-in shadow detail,
whether there’s a full range of tones, and how
light or dark the image is overall. It’s basically a
bar chart (though with so many bars they
blend into a continuous curve) showing how
many pixels there are for each brightness value
across the tonal scale, from dense black to
brilliant white.

The perfect spread of tones
You may hear people talk about the ‘ideal’
histogram, but in practice histograms can come
in many different shapes, depending on the tonal
balance in the image. What you would want to
see in a histogram, though, is the histogram
curve tailing off to zero more or less exactly at      or blocked-in, detail-free shadows in the image. If
the far left-hand (shadow) end of the scale and        the histogram is chopped off at the right, you’ve
again at the far right (highlight) end. That’s         got ‘blown’ highlights, which are areas of
exactly what we’ve got with our sample shot            featureless white. If the histogram’s been chopped
here. However, if the histogram is chopped off at      off, or ‘clipped’ at either end, there’s nothing you
the left, that means there are areas of solid black,   can do to bring that image detail back.


32                  Exposure
Exposure   33
     Unusual histogram shapes
 The ‘typical’ histogram tails off at the left and
 right-hand ends, but swells to a maximum
 somewhere round the middle. Some subjects,
 though, produce very different results. If you
 shoot a shadowed subject against a bright sky,
 you might get two ‘peaks’, one in the shadows,
 one in the highlights,
 and practically nothing
 in the middle. There’s
 nothing wrong with
 your exposure
 technique, it’s just
 characteristic of this
 type of subject.




                                                              ‘Flat’ histograms
                                                     On overcast days, or in other situations where
                                                     there’s not a lot of contrast, you might end up
                                                     with a histogram that tails off to zero long before
                                                     the left and right-hand ends of the scale. This is a
                                                     characteristic of flat-looking images. As the
                                                     histogram shows, there are no really dark or
                                                                                   really light areas,
                                                                                   which is a problem
                                                                                   because photographs
                                                                                   usually rely on a full
                                                                                   range of tones for
                                                                                   depth and richness.




34                Exposure
                                                         Clipped shadows
                                                 Histograms can reveal obvious flaws in your
                                                 images. This shot has been underexposed, and
                                                 this has moved the whole histogram to the left,
                                                 with the result that the shadows have been badly
                                                 clipped, while there are no real bright highlights
                                                 (the histogram doesn’t reach the right-hand end
                                                                               of the scale). You
                                                                               can adjust the image
                                                                               in Photoshop to
                                                                               restore brilliant
                                                                               white highlights,
                                                                               but you can’t do
                                                                               anything about
                                                                               those lost shadows.




       Clipped highlights
This image has the opposite problem. It’s been
overexposed, with the result that the whole
image histogram has effectively been moved to
the right. Even though we’ve recorded the
shadow detail nicely, the highlight end of the
histogram has been
clipped, just as the
histogram curve is
rising, indicating the
presence of lots of
bright tones in the
sky. These tones can’t
be recovered.




                                                                         Exposure                     35
Controlling the dynamic range
E     arlier, we mentioned the idea of dynamic range – the
      range of tones your digital camera’s sensor can record. This
ties in with our look at histograms in the previous section. You
                                                                     Before

can think of your camera’s dynamic range as an ‘exposure
window’. Your job is to try to get the full range of tones in your
subject into this window. As we’ve seen, if the brightness range
is too high, you have to decide whether to sacrifice extreme
highlight or shadow detail, depending on what you consider to
be the main subject. This isn’t the only alternative, though.
There are things you can do to reduce the contrast range in the
scene at the time of shooting.




                          Fill flash is a useful way of
                 ‘balancing’ extremely high contrast
                     scenes, but it only works on subjects
                 within the range of the flash, typically 2-
                               4 metres for a built-in flash.


36                  Exposure
        Using balanced fill flash
After   Outdoor portraits are often difficult to pull off
        successfully, especially in bright sunlight. If you
        face your subject towards the sun you reduce the
        contrast range but you make them squint. If you
        position them side-one, you get ugly shadows
        across their face. And if you shoot them with their
        back to the light, you have the problem that their
        face is in shadow against a bright background.
        However, if you set your camera’s flash to forced
        flash mode, and as long as your subject’s just a
        metre or so away, it can provide enough ‘fill light’
        to even up the tones. You can use fill flash
        indoors, too, as we have here, to balance up dim
        indoor lighting against bright daylight outside. If
        your camera has a ‘slow sync’ mode, you can
        create interesting flash effects at dusk, too,
        illuminating nearby objects against a colourful
        sunset or twilit sky.




                            Exposure                    37
Using a neutral density grad
Landscape photographers often struggle with bright
                                                           Without Filter
skies, particularly on overcast days, where the sky
acts, in a sense, as a vast, diffused light source – and
one which is 2 EV to 3 EV brighter than the
foreground. You have a dilemma. Either you expose
for the foreground and risk the sky bleaching out to a
featureless white, or you expose for the sky and hope
you can drag up enough detail from the dark
foreground in your image-editor. If the brightness
range is too great (it often is), you need another
solution. For this shot, we’ve used a ‘neutral density
grad’, a filter which is darker at the top than the
bottom. By positioning this carefully in the filter
holder, we’ve darkened the sky enough to even up the
exposure, but without affecting the foreground.
   Graduated neutral density filters come in various
strengths, which you can match to the brightness
range of the scene. It’s largely a matter of personal
taste though – do you like the heavily filtered ‘moody’
look, or something more natural? They also come in
both soft-edged and hard-edged forms. The soft-
edged sort can intrude intro areas of the frame you
don’t want to reduce in brightness (the top of a hill
that’s protruding into the sky, say), but the hard-
edged ones demand even more careful positioning.
   To get the most from a neutral density grad, you
really need a digital SLR, though filter maker Cokin
does supply an adaptor kit for digital compacts.




                                                                   A graduated neutral density filter solves
                                                               the problem we had with clipped highlights
                                                                  in our landscape shot. It reduces the exposure
                                                                   in the sky area by a factor of 4 (2 EV) to bring
                                                                            it within the sensor’s dynamic range.


38                  Exposure
With Filter




              Exposure   39
Using Photoshop                                                        After
Photoshop CS and Elements 3 have a Shadow/Highlight tool
for balancing the tonal values in high-contrast scenes. It works     We needed to reduce the
by selecting the darker areas only and then lightening them.         exposure by a massive 6 EV in
The results can look a little artificial if you’re not careful (you   our second shot, the one
need a large Radius setting, which blends the effect more            being used to record the dusk
subtly), but they can also improve shots considerably. This will     sky in this beach scene. The
only work, though, if the image contains a full range of tones in    blended image records a
the first place. If the shadow or highlight detail has been           dynamic range impossible to
clipped, there’s no getting it back. For scenes with too high a      capture in any other way.
contrast range for this approach, there is an alternative. You
can take two shots at two very different exposure values – one
aimed at capturing shadow detail, and one aimed at capturing
highlight detail – then blend them in Photoshop. Our
walkthrough shows you one way of doing this. (You’ll need to
use a tripod to ensure the images align exactly.)



     Before




40                  Exposure
1Combine the shots
     The first thing to do is add the lighter
exposure to the darker one as a new layer. You
                                                   2Blend the exposures
                                                        Now use the Colour Range command and
                                                   select Highlights from the pop-up menu. You’ll
                                                                                                    3Blur the transition
                                                                                                         The transition between the two image
                                                                                                    layers is too abrupt at the moment, but the way
can do this by using the Move tool to drag it on   need to make sure the Invert box is checked.     to fix that is to blur the layer mask. Making sure
to the other image’s window. If you hold down      Close the dialog box, and click the Add Layer    the mask is selected in the Layers palette, try a
the Shift key as you do it, the image will align   Mask button in the Layers palette. This will     Gaussian Blur of 250 pixels (less for lower-
automatically.                                     mask the bleached-out areas in the top layer.    resolution images).



                                                                                                                 Composition                      41
Master of
exposure
Pål Hermansen

L    ike many great photographers of the natural
     world, Pål Hermansen started his working life
doing something else. Born in 1955 in Oslo, Norway,
he trained as a dentist and homeopath, but was an
enthusiastic photographer from an early age. He
decided to turn his hobby into a career in 1971, when
he became a freelance photographer and writer.
As well producing numerous books, his striking work
has earned him international acclaim and many
awards. His images stand out from the norm because
of their exquisite portrayal of light and creative
compositions. He attempts to go beyond documentary
-style photographs to create something more artistic,
admitting that he perhaps ‘leans more toward the
photographic equivalent of poetry’.




42                Exposure
            This shot of black-legged
            kittiwakes, taken on Norway’s
            Lofoten Islands, proves that
sometimes, searching for the ‘perfect’
exposure isn’t always desirable. Would
this picture have as much impact if it
had a more neutral composition and
exposure? Notice how the soft edges of
the bird that’s out of focus work in
combination with its overexposed white
feathers to make it almost glow. It’s an
image that provokes extreme reactions –
you’ll either love it or hate it.




     Intrigued by Pål’s work? See
     more in the galleries at
palhermansen.com.


            Exposure                  43
Low light exposures
S    hooting at night is easy, it just needs much
     longer exposures than you’re used to in the
daytime. You could increase your camera’s ISO to
its maximum and try shooting handheld, but the
image quality will drop through the floor, and
shutter speeds will still be so long that camera shake
is nigh-on inevitable. The best approach is to use a
tripod, reduce the ISO to its minimum (to maximise
image quality) and experiment. Yes, experiment.
While your camera is perfectly happy with the
long exposures needed at night, its metering
system is likely to be all at sea when faced with
the naked light sources and much higher contrast
levels after dark.

Exposing in the dark
There are two approaches to working out exposures
at night. There’s the ‘it ought to be possible to work
this out’ approach, and the ‘I give up, let’s just suck
it and see approach’. The technical approach would
be to take a spot reading from a representative area
of the scene like a floodlit building, but excluding
any naked light sources. This is time-consuming and
error-prone. The simplest route is to start with an
exposure of 4 seconds at f/5.6 for a typical city
scene, see how it comes out, then reshoot with
different settings. There is one thing to beware of,
though. Your camera’s LCD will appear much
brighter at night, so that while an image may look
good when played back at the time, it can prove to
be hopelessly underexposed when you get it on to
your computer. Instead, use your camera’s
histogram display to check the tonal distribution –
this is a much better guide.


44                  Exposure
      Night photography presents special
      exposure challenges. Often a purely
experimental approach is the quickest and
best solution.




How to control noise
Noise can be more of a problem with night shots,
and there are reasons for this. First, if you don’t
manually set your camera to a low ISO, it will
automatically increase the sensitivity in response
to the lower light levels. Auto ISO is a default
option with compact cameras especially. Second,
long exposures tend to encourage more sensor
noise. However, makers now incorporate
effective noise-reduction systems that kick in
automatically with longer exposures. Check
whether your camera does this, or whether you
have to enable noise reduction manually. Third,
noise tends to be more apparent in darker areas,
and night shots can contain large expanses of
black or dark tones. You can reduce noise in
Photoshop and other image-editors, but only at
the cost of some fine image detail. The Dust &
Scratches filter is probably the most usable and
controllable tool for this.




                     Exposure                   45
High key/low key
T     he concept of the ‘ideal’ histogram can be
      useful when choosing exposure settings and
evaluating images, but it’s a mistake to imagine that
                                                        High key
all images must conform to this even distribution of
tones. Intrinsically light subjects, for example, can
be expected to produce histograms where the tones
are clustered up around the right-hand (highlight)
end of the scale, whereas dark subjects should
produce histograms shifted towards the darker, left
end. This is exactly how these subjects should look.
Deliberately light images are called ‘high key’
photos, while dark shots are ‘low key’.




46                 Exposure
                You can do effective high key and
Low key         low key portraits using either natural
          or artificial light.




          Going to extremes
          You can take high key and low key exposures to
          extremes, and produce striking and creative
          results. For example, if you place a fair-skinned
          model against a bright background, and use an
          exposure which just captures the details of the
          face at the highlight end of your camera’s
          dynamic range, the result will have a brilliant,
          ethereal quality. Or, to produce a far more
          sombre, dramatic portrait, you need to choose a
          dark background, contrasty lighting, and set an
          exposure that records the highlights on the
          subject’s face but the shadowed side and the
          background as very dark, near-black tones.
          The histograms for these images will be very
          far from the ‘ideal’ shape, and may also have
          clipped highlight or shadow detail.
          Nevertheless, they can work very well as
          photographs. The point about histograms is
          that they simply tell you what the image is like –
          they’re a diagnostic tool. They’re not there to tell
          you what the image ought to be like. That’s your
          job as the photographer.




                                Exposure                    47
 Master
Exposure
       Top 10 tips...
      TAKE A MID-TONE WITH YOU                       RESTORE THE WHITENESS

 1    Pack a grey card in your camera
      bag – or buy a mid-toned camera
 bag which you can meter off.
                                               6     If your subject’s large in the frame
                                                     and bright white, spot meter off
                                               them and add 2 EV to 2.5 EV.

       LOOK AT THE HISTOGRAM                         METER FOR HIGHLIGHTS

 2     Don’t rely on a simple playback
       image to judge exposure – let the
 camera show you precisely…
                                               7     As a general rule, it’s best to meter
                                                     for the highlights and let the
                                               shadows fall where they will.

       WATCH THE BACKGROUND                            CARRY A SET OF FILTERS

 3     Be aware of how the tone of a
       background can influence your
 camera’s meter.
                                               8       Always pack a graduated neutral
                                                       density filter and polariser – they’re
                                               not just useful for ‘pure’ landscapes…

        BE AWARE OF HIGHLIGHTS                         DIAL DOWN YOUR FILL FLASH

 4      When exposing for dark subjects,
        look for any bright areas that
 might be blown out as a result.
                                               9       With digital cameras so good at
                                                       picking up shadow detail, you’ll be
                                               surprised how little fill flash you need.

        SWITCH TO SPOT METERING                            GET CREATIVE

 5      For tricky lighting and small areas,
        there’s no substitute for spot
 metering if you’re not in a rush.
                                               10          Don’t always chase the
                                                           ‘perfect’ exposure.
                                               Experiment with going to extremes.




                                                                                               Exposure   49

								
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