Night Photography Part 2

How to Expose for the Night

Night photography is one area where you can forget about multi matrix, spot, honeycombs any other metering system!

Why? Because the only good light meter for night photography is your eye and experience. Because we are no longer dealing with daylight, a metered reading can only be used as a "starting point". There are a few factors in night photography that make camera meters unreliable. Exposure meters work on the premise that the area being read contains equal amounts of light and dark areas. It can then integrate the reading to a tone of gray. 90% of the time this works fine and experience (or one of our courses) will tell you when meters are not 100% accurate. For example, large amounts of dark unlit areas with small bright points of street lighting being one of them.

In most night situations it's best to start with a shutter speed of about 2 seconds with a mid range aperture of roughly f5.6 if depth of field is not a priority. If the exposure has to be lengthened, use the shutter. If your camera has shutter speeds of up to 30 seconds, use the Self Timer to fire the shutter. If your camera does not have such long shutter speeds and the situation requires it, use the "B" setting. In this case though it is strongly recommended to use some form of remote release.

Film and Sensitivity Ratings

It is a common belief that the lower the available light, the faster the film or sensitivity rating needs to be to get enough light onto the film/sensor. Usually this is true, however, fast films or ISO settings (i.e. 400 ISO/ASA and over) are not always necessary for night shots.

There may be an occasion when this effect is desired for night photography, but on the whole fast film is not necessary. In fact a slow speed film can be used just as effectively, the exposures needed would just be that bit longer, sometimes for several seconds. Hence the need for a sturdy support such as a tripod!

With film cameras any type of film is suitable for night photography, but slide film will generally show the best results. Color print film is fine but sometimes when there are very dark areas in the image, commercial processing machines may produce poor prints. Be warned, just because the print you get back from your processor looks grey and dull, doesn't mean the image was exposed poorly. Often the negative would have to be inspected to confirm the images exposure accuracy.

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Reciprocity Law Failure

Although the reciprocity law failure effect can take place with daylight photography, the long shutter exposures of night photography definitely suffer from this. Reciprocity Law failure is the loss in the exposure sensitivity of the film. This is caused by either a prolonged exposure period (more than 1/10 sec. shutter speed) or an extremely brief period of the shutter opening (shutter speeds faster than 1/2000 sec.).

As a brief example, if a film rated at 100 ASA was exposed for 2 sec. its film speed rating could fall to 50 ASA. What this leads to is underexposure if the image was taken at the camera meters correct exposure reading. Exposure meters do not take into account reciprocity law failure. With color film the colours would also be affected giving a slight colour cast to the image. It is very difficult to allow for reciprocity failure as different films and even different batches of the same film react differently under these conditions.

Digital images do not suffer from reciprocity law failure. However because of such low resolution compared with film, highlight areas will burn out much more prominently in the image.

As a very general guide use the following table.

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Exposure Bracketing

For night photography it is best to take four or five images of the same scene at different exposures. This is called Exposure Bracketing. With digital cameras, even though you can inspect your results on site, its best to bracket and save the images as well. LCD monitors are generally so small that a true account of the image can't be achieved until the images are viewed on the computer screen. A good starting point is a general meter reading.

If you are handy with a spot meter or working out an exposure by reading different areas of a scene, this type of starting point could be more accurate.

It is recommended that the correct reading given by the meter should be the shortest exposure. For a meter reading of 2 seconds for example, the other exposures should be stepped up 1 stop for each exposure. This would mean that the other exposures would be; 4 seconds, 8 seconds, 16 seconds and 32 seconds. With a bit of experience (and luck!), one of these images will have the most pleasing results.

When faced with a night-time image, the first thing the photographer should decide is what part of the image he/she wants properly exposed. This is especially important when dealing with mixed lighting. Once this has been decided, take an exposure reading off the desired area. Do this by filling the viewfinder of the camera with as much of this area as possible. Either by moving closer and measuring the exposure, using a longer lens or using a spot meter. Recompose the image and then bracket the exposures.

Artificial Lighting

Camera meters are designed for use in daylight conditions. Artificial lighting has many different aspects and there are many different types of artificial lighting. To the human eye the lighting may seem bright and white but to film it is much weaker and coloured. Household tungsten lighting for example, has a yellow/orange cast while fluorescent lighting has a green cast. A typical night image may have numerous different types of light sources lighting the scene (fig n-8). These would be of different strengths and colours. This fact of course adds to the impact of the night photograph, but is not always desired.

Color temperature filters can be used to help change coloured artificial lighting to a better 'white' balance closer to what we perceive it to be. For example a blue filter would be used to counteract the warm cast of tungsten lighting.

Many digital cameras have a white balance feature that act in much the same way as filters for film. Fig n-8 and n-9 above were taken with a digital camera. The uncorrected version (fig n-8) was balanced for daylight, the same as using daylight balanced color film. Fig n-9 was corrected for the tungsten lighting, the same as using a blue filter for daylight film or using tungsten balanced film (note the very strong blue cast in the image). Which is the better result is really a matter of taste. Often though the warm cast of artificial lighting is preferred.

fig n-10 Multiple Color Casts

In situations where many different types of light sources are present, it would be impossible to correct the color casts (fig n-10). Even doing so would most likely reduce the impact of the image created by the different coloured lighting.

Fig n-10 was taken in Downtown Disney in Disney world Florida. There are many different light sources including fluorescent (green lighting), halogen tungsten (orange lighting) and many different coloured neon signs. All add to the impact of the final image and if any where corrected, the other colours would be changed.

You will find that metering off light sources, for example lighted or neon signs will give a much faster exposure then reflected light from street lighting or floodlight. Although a meter reading may be a fair starting point, a certain amount of experience can go a long way. As you gain your experience with night photography you will find that your instincts in estimating an exposure will surpass any camera meters capability.

Extremes of Lighting

fig n-11 Direct and Reflected light

An important factor in night photography is how the lighting is portrayed in the scene. When portraying rows of street lighting for example, the direct light source itself is being photographed, therefore the lighting being exposed is very bright. An image of a floodlit building on the other hand is an image exposed by reflected light. This naturally is much weaker and would need a much longer exposure.

In many cases the two examples would be portrayed in the same image, this would lead to extreme contrasts and very difficult exposure metering problems. In a case like this it is always best to expose for the reflected light and ignore any lighting that is portrayed in the image. Doing this will no doubt lead to overexposure of the light fixtures, but this can look quite acceptable in the image.

Fig n-11 was taken of an Irish pub would have been underexposed had the meter reading given be used. The strong flood lighting would have been the only detail in the image, leaving the rest of the image black. The photographer has decided that the stone detail is an important feature to capture.

An exposure of 8 seconds at f11 was used to record the light reflected off the building. Even though this exposure overexposed the flood lighting, it still doesn't take from the image. Hand printing can 'burn in' areas that are over-exposed to help balance the image.

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Using Movement

With extremely low light levels, moving subjects such as people walking will not register on film so long as there is very little light shining upon them. Cars are a good example of using this technique. With long shutter speeds and moving cars, the headlights and taillights will register on film as streaks. The cars themselves will not register on the film. This effect can also be used at fairgrounds where amusements lighting can be recorded on film while moving.

In fig n-12, an exposure of 30 seconds at f16 was used. The long shutter time allowed the cars to move fully through the frame leaving their headlights and taillights to "streak" through the frame. Notice that detail from the cars did not register in the image. Since there was some ambient lighting in the sky and street lighting, a high f-number was used to keep the scene from overexposing.

In fig n-13 a different approach was taken. Instead of mounting the camera on solid ground it was "taken for a ride". In this image the camera was mounted on a tripod positioned in the backseat of a car. As the car was driven an exposure of 30 seconds was used. As the car moved the street lighting and oncoming cars headlights registered on film and drew "streaks" across the image. The driver, viewed in the rear-view mirror, was lit with a flashgun that was used off camera and directed at his face.

Warning - Firing a flashgun at a person while driving may blind them temporarily, even from outside the car. This is a dangerous technique that should be carried out carefully with the drivers knowledge and consent.

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