Working With Light At Night

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.