Being able to control the
interplay between light and shadow is a skill that separates great
photographers from mere mortals. When it comes to night photography
there are so many different light sources to deal with it can
be overwhelming for even the seasoned pro.
In my previous tutorial I explored the different subjects you can shoot at night. In this tutorial we'll look at the different sources of light that illuminate these
subjects or are light sources themselves.
Challenge and Reward
The
first night photography picture that I was
truly happy with was a photograph of the Henley Beach jetty taken
around sunset. It was primarily the mixture of light sources and the
colour in the scene that held my interest. The low-light conditions at
twilight, no tripod, and a slow film also made
capturing this image quite challenging. I felt as though my
efforts had been rewarded, though, when I finally saw the shot after it
was processed. The
warm intense colours of the evening sky along with the artificial light
sources present elevated this image from its rather average
composition.The
mixture of artificial and natural light sources is something that you
will have to deal with in many night photography scenarios.
Understanding some basic principles about the light in each scene is one
of the challenges of this discipline.
There are many different types of
light sources and each will have a different colour temperature value.
Colour temperature is a method of describing the color
properties of light, as either a warm yellow hue or a cool blue hue with
a value assigned in Kelvin.
Artificial Lights
Tungsten
or incandescent lights have a color temperature value of approximately
3200 Kelvin and are considered to be a "warm" light source. They
are a very common form of lighting and are used in many types of
applications such as car headlights.
Sodium vapour
lights have an even warmer colour temperature of approximately 2500
Kelvin and appear as an orange-coloured light source. They are
commonly used in street lighting and industrial applications like
factories and shipping yards.
Subjects illuminated by sodium vapour lamps are very difficult to colour
balance accurately. These are the lights that give cities their characteristic orange glow
when seen from a distance. Sodium
vapour lamps illuminate this factory scene. The mix of cool blue light
from the sky at twilight compliment the warmer tones of the sodium vapor
lights.Neon
or fluorescent lights are another very common form of lighting. They
have
a colour temperature of around 4000 Kelvin and exhibit a green
colour cast. They work by ionizing a gas which then fluoresces, emitting
light. They are used in many different lighting applications such
as streetlamps
and indoor lighting.
Some forms of lighting, such as
sodium vapour and fluorescent, flicker at a frequency
equivalent to the power supply being used. AC is an acronym for
"alternating current" and these types of power supplies alternate
phase of this current causing these light sources to
rapidly switch on and off.
If a 110 volt power supply is present the
frequency of this flickering happens at 60 hertz or 60 cycles a second.
Power supplies that output 220 / 240 volt have a frequency of 50 hertz and
flicker at 50 cycles a second.
For photography
this isn't really an issue but if you are shooting video with these
light sources present you will need to synchronise your shutter speed
with the frequency of the power supply or artifacts from this
flickering can ruin your footage. For 240 volt AC power you need to use
1/50th of a second and for 110 volt systems instead chose 1/60th of a second.
Natural Light
The colour temperature of sunlight varies over time,
with cooler values of around 5500 Kelvin at midday when
the sun is directly overhead. At sunrise and
sunset, when the sun's rays have to pass through a thicker layer of the
earths atmosphere, light is refracted towards the red end of the spectrum
producing warmer hues.
This effect also happens with moonlight.
Warmer
colour temperatures occur when the moon is near the horizon. Moonlight
is essentially sunlight reflected off the surface of the moon and this
light can provide plenty of illumination for landscape images,
especially around the time of the full moon. Starlight can also provide light for landscape or seascape images but light sources this dim require very long exposure times.The
variation in colour temperature between artificial and natural light
sources can make getting accurate colour very tricky - especially when
you have a mixture of these different light sources in the same photo.
Starlight
and the toxic orange glow of a town in the distance co-exist in this
single image. The two light sources balance out with the cool tones of
the sky complimenting the orange glow of the city.The
above example illustrates why I recommend you shoot using a RAW image
format. Recording the raw image data from your camera's sensor allows
you to adjust colour balance after the photograph has been taken. If you
choose to shoot another image format such as JPEG, your colour is
essentially set and it is far more difficult to adjust colour
values later.
Twilight
Twilight is
one of the best times to
take night photographs. It is often referred to as
"blue hour" as the sky turns a rich deep blue colour. During this
transition period from day to
night colour balance shifts dramatically. It can be tricky to choose a
colour balance when you try to mix twilight with artificial light
sources from a cityscape and deal with a rapidly changing lighting
scenario. In this situation shooting RAW will allow greater colour
processing flexibility. This
image contains a mixture of artificial and natural light sources and
was taken at twilight. By shooting RAW I was able to process colour in
Photoshop precisely how I wanted. RAW conversion software allows white
balance selection after the image has been captured. If I had elected to
shoot this image as a JPEG or TIFF file I would not have had the same
flexibility in colour processing.
Film and Digital Media at Night
If
you choose to photograph on film you are also limited in your options for colour
processing. Film stocks have colour balance incorporated into their
chemistry and you choose between different film varieties according to
the prevailing lighting conditions. If you choose to use a film stock
designed for tungsten lighting in daylight conditions your colour
balance will shift towards a cooler tone, making the whole picture appear
too blue.
With film you can compensate for
colour balance discrepancies to a degree by using colour conversion
filters but this is far from a perfect solution. Digital imaging
technology offers far more flexibility in colour processing. With digital you also have
the benefit of instant feedback and can see your results immediately on
the cameras LCD screen. I'll cover the advantages and disadvantages of both technologies in more depth in my next tutorial.
One thing
to keep in mind with different colour temperature light sources is that
the focus point changes due to the different wavelengths of light. This
effect is quite obvious in certain photographic situations like an
indoor event such as a concert. If there is a rapid change from a red
light source to a blue light source your focus point will shift. If you
like to do candid street photography at night this focus shift can make your job
more difficult especially if you find yourself in a situation where the
light sources are constantly changing such as flashing neon lights.
Conclusion
One
of the main difficulties of photographing at night is the infinite
variations in colour different light sources create. I try to think of
there light sources as a creative challenge, and I encourage you to
think that way too: embrace experimentation with night photography
subjects, take some risks and see what you end up with. Spend some time
exploring these different light sources, especially during the
transition period from daylight to night time.
Challenging mixed
lighting can usually be overcome by shooting RAW format digital files.
Adjusting the colour balance later using your RAW processing software of
choice works well in most situations. Don't limit your options -
experimentation is the key! When you expose your pictures well you can
almost always post-process your photos exactly how you like - adding a
unique flavour and individual element to your image making.
See
you in the next tutorial! I will be investigating the use of film and
digital cameras and the pros and cons of these two different
picture-making media.