Photography

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Published: Sunday, 11 March 2018 07:54

Night photography

 Introduction

I have enjoyed photographing night creatures for over 35 years. With the rapid advancement in camera technology and LED illumination it is now possible to photograph birds flying at night and my techniques and equipment have evolved during those years. For this type of photography, the additional equipment can be as simple as a decent spotlight plus assistant or as complex as you wish. These are my thoughts and techniques as of February 2021.


Illumination

Photography in darkness requires either a continuous light source or electronic flash. There are several important differences between daylight and light sources which a night photographer needs to understand.

A fundamental of light is that the brightness of an illuminated subject, decreases in proportion to the square of the distance from the light source. For daylight photography, this fundamental can be ignored because the distance of the photographer does not change the brightness of the subject. When illuminated with artificial light, however, this is not the case as the diagram below illustrates. The diagram shows an object located at distance "d" is four times brighter than an object located twice as far away at distance "2d". Consequently, if the subject distance from the light source is doubled, the exposure needs to be increased by the equivalent of two f-stops and if it is halved, the exposure needs to be reduced by the equivalent of two f-stops.

 






Continuous lighting  - such as a spotlights is great for photographing stationary animals. Filament lamps and Xenon arc lamps produce light of excellent colour quality but are heavy and power hungry. LED spotlights and flashlights are portable, bright and energy efficient but most products produce light of poor colour quality. High colour quality LED lights having a high colour rendering index (CRI)  are becoming available and produce excellent results at comparable prices.

Exposure is determined using the camera metering system by adjusting shutter speed, aperture and ISO. The Tawny frogmouth below, was lit with the car high beam with camera settings of 1/15s, f5.3 and 9,000 ISO.

 

Electronic flash - is the ideal portable light source because it emits an extremely intense burst of light that can freeze movement of fast moving subjects. Flash units contain complex electronics that produce a short electrical discharge inside a transparent tube and when sufficient light has been emitted, the discharge is terminated by the clever electronics. The flash-tube contains xenon gas which produces intense white light of very high colour quality. Most models have auto-mode, however I prefer manual mode which controls the light output in f-stop increments.

To illustrate the advantage of manual flash over continuous light sources in freezing motion, I photographed an operating ceiling fan, with with black lines painted on one blade, at different shutter speeds and with different flash settings. Images in the top row were taken using a spotlight and camera shutter speeds from 1/500s  to 1/4000s. The bottom row was taken using a fixed shutter speed of 1/200s and electronic flash on power settings from full power to 1/32 power. Comparison of the images reveals that 1/4,000s shutter speed is equivalent to a flash flash power setting of 1/4 and the 1/32 power setting is estimated to be equivalent to a shutter speed of 1/20,000s.


Flash extender - With a telephoto lens at night, a fresnel lens located in front of the flash concentrates the light output providing a 3 f-stop gain in brightness. To illustrate this, the images below were taken using a 50mm lens with identical camera/flash settings and processing. The flash extender reduces the beam angle to produce a 'hotspot' which can be difficult to keep aligned when using a long telephoto lens.


 

Focusing at night

The different types of focus sensors in DSLR and in mirrorless cameras essentially measure subject contrast. The camera continually adjusts the lens focus until maximum contrast is obtained. Illumination intensity, subject contrast and movement, each affect the camera's ability to focus accurately and quickly and at night, high intensity illumination is necessary.

LED flashlights and bicycle headlamps provide sufficient light output to focus well on stationary subjects at night, however flying birds require much higher intensity. The human eye is a poor judge of light intensity and what may appear to be bright to the photographer may in fact be photographically very dim.


Exposure determination

With a continuous light source such as a spotlight, obtaining the correct exposure is identical to day-time photography.

Using flash, the task is more difficult. I set the flash mode to manual power because auto-flash usually produces disappointing results outside at night.

At the commencement of a night outing, I "calibrate" my camera/flash by taking a few test shots of an object such as a tree trunk, at a "typical" distance. My flash (with flash extender) set on 1/4 power, f8 and ISO 800 achieves good range and motion stopping ability at a distance of 10 metres.

For a different distance I adjust the ISO, aperture and flash power accordingly and where possible take images at different exposures.

 

Gear for night

When working from a car or with an assistant, photography in the dark is straightforward. When alone, simple tasks including, changing settings, and adjusting gear are difficult and error prone. It is a great help to pre-configure as many settings as possible and get your gear ready before nightfall. My current setup shown below  consists of a rigid carbon fibre bracket containing a rechargeable spotlight and TTL cable and weighs 750g. On maximum power, the spotlight produces 700 lux at a distance of 10m which makes it possible to lock focus on birds flying at night at distances of at least 20m.

 
 

Tripod - A tripod is a useful adjunct for photographing at fixed locations such as roosts or nests. A small lightweight carbon-fibre tripod to support the camera or as a stand for an off-camera flash is ideal.

Slaves and triggers - Occasionally, I use off-camera flash triggered by sync. cables or Pocket Wizzard Plus-X radio triggers. Previously, I used Nikon's clever inbuilt 'CLS' system which uses line of sight infrared communication between camera and flash. Unfortunately, it is time consuming to set up and unreliable in the bush due to  beam path obstructions from unseen objects such as leaves and branches.

 

Camera settings

Settings Banks - Many cameras allow you to save your favourite settings for quick recall. My camera has two banks which I have configured for night use, one for flying birds and the other for stationary subjects. It saves enormous time and frustration being able to select pre-configured settings by simply rotating a knob.

Image format - RAW file format has high dynamic range and a high capacity for correcting white balance and for salvaging shots which would have been spoilt by over or under exposure had they been taken in jpeg format.


LCD Monitor - At night the monitor screen appears very much brighter than it does during the day and images which appear adequately exposed are often seriously underexposed. To counteract this, I turn the monitor brightness right down and where possible check the image histogram after the exposure.

 
Shooting Mode - My camera is always set to manual mode because I always use manual flash at night.


Focus - For stationary birds I use the centre autofocus point and continuous focus with the camera set for 'backbutton autofocus'. Backbutton focussing makes it easy to reframe the subject without  refocusing. For flying birds, I use continuous autofocus and multiple focus points, with the shutter shutter release button set to "focus and shoot". Camera brands and models have a multitude of focus modes and I am not sufficiently knowledgeable to expound on which ones are optimal.


ISO - Producing sufficient light to properly expose the image or to obtain a 'motion-free' image can be difficult. Using higher ISO is equivalent to using a more powerful flash unit, however the downside is that it increases image noise. On my camera ISO 800 produces an acceptable level of noise and I use that as my go-to night setting.


Aperture - A wide aperture is often desirable to isolate the subject from the background and increase the maximum working range of the flash. The downside is that accurate focus is even more critical and some lenses are softer at their widest aperture.


Shutter - When using a camera with focal plane shutter, the maximum shutter speed should not be set higher than the maximum flash sync speed, which is around 1/200s for most models. At night, the surrounds are dark and it is the short duration of the the flash which stops motion, not the camera shutter speed.

Slow shutter speed in low light can be useful for stationary subjects to record ambient light as shown for the Barking owl below, which was taken at 1/15s. The owl remained sharp because it was exposed by the flash, whilst the background shows some blur from hand-held camera movement.

 


Illusion of speed - Flash combined with low shutter speed can be used
to give the illusion of speed. For the Nightjar below, a sharp image of the bird was produced by the short duration of the flash which is superimposed on a blurry image produced by the slow 1/30s shutter speed and the focus light. By setting the camera flash mode to 'rear-curtain sync', the blurred image trails the bird giving the impression of speed.

 

 

This technique is often a bit of a gamble as a potentially good image of a difficult to photograph subject, such as the Grass owl with prey below, is ruined.

 

 

Nocturnal Eyes

Pupils - A continuous light always produces contracted pupils when the bird is looking toward it and there is no way to prevent that. This is especially noticeable for a bird having a light coloured iris such as the young Boobook owl on the left below. Large eyes are a prominent feature of nocturnal birds and if we were able see in the dark we would see that their pupils are always wide open. To me, dilated pupils look natural and can be captured by pre-focusing then turning off the focus light a couple of seconds before releasing the shutter, as shown for the Boobook on the right below.

 

Red-eye

Red-eye occurs when the light source is located 'close' to the camera and light is reflected from the retina of the eye into the camera lens. By moving the light source away from the camera or moving closer to the subject red-eye can be reduced or avoided. This is illustrated in the diagram below and in the images of a Tasmanian Boobook owl, taken at different distances and head angles. Increasing the angle can be achieved via a camera bracket or using off-camera flash.


 

Sometimes you cannot avoid red-eye as seen in the left and centre images above, however it can often be 'fixed' by photo-editing. Pupils almost always have some light and colour, so I prefer to darken them by 'burning' the shadows and mid-tones, then desaturating the colour until they are almost black. You can also 'dodge' the catchlights and eye reflections to enhance their appearance as shown for the same images below.

 

 

Flying birds

Flying birds present the ultimate challenge. Sharp images can be obtained by shooting a bird leaving or arriving at a pre-focused destination or by achieving focus in flight. The Tawny frogmouth below was taken by pre-focusing on the perch it was using for hunting and by watching with a dim red light until it flew. The Grass owl was focused in flight using the camera bracket detailed above.

 Conclusion

My thoughts and ideas are intended as a guide for those interested in night photography. They should not be considered binding, rather as ideas and techniques that have worked for me and can be improved upon. I hope this article can assist you in developing yours night photography skills and encourage you to give it a go.