Photography

Category: Pages
Published: Sunday, 11 March 2018 07:54

Night photography

 Introduction

I have enjoyed photographing night creatures for over 30 years and my ideas and equipment have continually evolved. With the rapid advancement in camera technology and the advent of LED illumination it is now possible to photograph birds flying at night. This trend will continue and the techniques and equipment I use today will quickly become outdated. For those interested in this type of photography the additional equipment that is needed can be as simple as a decent spotlight and an assistant or as complex as you wish. These are my thoughts and techniques as of September 2019, which I hope will provide insight and tempt you to venture out at night and enjoy your photography in a different light.


Illumination

Photography in darkness requires artificial light in the form of either a continuous light source or electronic flash. There are several important differences between daylight and light sources which the experienced night photographer understands.

A fundamental characteristic of light is that the brightness of an illuminated object, decreases in proportion to the square of the objects distance from the light source. The diagram below shows that if an object is located at "d" it would be four times brighter than if it was located at "2d". Each time the distance to the light source is doubled, the exposure needs to be increased by the equivalent of two f-stops. Likewise, if the distance is halved the exposure needs to be reduced by the equivalent of two f-stops.

For outdoor photography during daylight, the sun is so far away from planet Earth that the brightness of an object in full sunlight is essentially constant and distance variations can be ignored. However, a photographer on planet Jupiter which is 5 times further away from the sun, would need to increase the exposure by 25 f-stops!






Continuous light sources  - such as spotlights are great for photographing animals that are stationary. Filament and Xenon arc lamps produce light of excellent colour quality but are power hungry and heavy by today's standards. LED lights are portable, bright and energy efficient  but most produce white light of  poor colour quality. High quality white LED's such as the Cree XHP series now include high CRI versions which are available at a reasonable price.

Exposure is determined using the camera metering system by adjusting shutter speed, aperture and ISO. The Tawny Frogmouth below, was sitting on a fence post and the car headlights were used for illumination with a camera setting of 1/15s, f5.3 and 9,000 ISO.

 

Electronic flash - may be considered the ideal portable light source because it emits an extremely intense burst of light of a high colour quality which can freeze a fast moving subject. Flash units contain complex electronics that produce a short electrical discharge inside a transparent tube. When sufficient light has been emitted, the discharge is terminated by the electronics. The flash-tube contains xenon gas which produces intense light having a white balance and CRI comparable with midday sunlight. Most models have an auto-mode, however I prefer manual power settings which control the light output in f-stop increments.

The composite image below is of an operating ceiling fan. One fanblade was painted on the edge with white paint and black lines. Images in the top row were taken using continuous light and show the effect of camera shutter speed in stopping motion. The bottom row, taken using an electronic flash on different power settings, using  a camera shutter speed of 1/200s, illustrates the superior motion stopping ability of flash. Comparison of the images also reveals that the maximum 1/4,000s shutter speed on my camera is equivalent to a power setting of 1/4 and the motion stopping ability of the 1/32 power setting is equivalent to a staggering shutter speed of around 1/20,000s.


Flash extender - With a telephoto lens at night, a fresnel lens placed in front of the flash can concentrate the light 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 bright  'hotspot'.


 

Focusing at night

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

LED flashlights and bicycle headlamps provide sufficient light output to focus on stationary subjects, however flying birds require much higher intensity. Note: the human eye is an extremely poor judge of intensity and what may appear to be bright may be photographically dull!


Exposure determination

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

Using flash, the task is more difficult. I set the flash mode to manual power because auto-flash often produces disappointing results when used 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 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 a few trial exposures.

 

Gear for night

When working from a car or with an assistant, photography in the dark is fairly straightforward. When alone, simple tasks such as changing camera settings, adjusting gear and lights 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 uses a  rigid DIY carbon-fibre bracket which attaches either to the camera baseplate (70-300 mm zoom) or the lens-foot (500 mm lens). On maximum power, the focus light produces 700 lux at a distance of 10m which makes it possible to lock focus on birds flying in the dark at distances >20m.

 
 

Tripod - A tripod is a useful adjunct for photographing subjects 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 the desired settings by simply rotating a knob.

Image format - RAW file format has a much higher capacity for correcting white balance and for salvaging great shots which would have been spoilt by over- or under exposure if the image files were .jpg.


LCD Monitor - At night the monitor screen appears very much brighter than it does during the day and often, images which look adequately exposed are seriously underexposed. I turn the monitor brightness right down and where possible check the image histogram to see if the exposure was OK.

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


Focus - For stationary birds I use the centre autofocus point, continuous focus and have the camera set for 'backbutton autofocus'. Backbutton focussing makes it easy to reframe the subject without  refocusing. For flying birds, I use continuous autofocus with multiple focus points selected and use the shutter release button 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 high ISO increases image noise. On my camera (Nikon D750) ISO 800 produces an acceptable level of image noise and I use it as my go-to night setting.


Aperture - Using a wide aperture is 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 pulse of light from the flash which stops motion, not the shutter speed.

Slow shutter speeds in low light, however, 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 detail an some blur from camera movement.

 


Illusion of speed - Flash combined with a low shutter speed can be used
to give the appearance 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 imaged produced by the slow 1/30s shutter speed and the focus light. By setting the camera flash mode to 'rear-curtain sync', the blurry images appears behind the bird. 

 

 

More often than not, this technique is a bit of a gamble as a potentially good image of difficult to photograph subject, such as the Grass owl with prey below, is ruined.

 

 

Nocturnal Eyes

Pupils - Unfortunately, a continuous light always produces contracted pupils when the bird is looking toward it. This is especially noticeable with birds having a light coloured iris such as the young Boobook owl below on the left. Large eyes are a prominent feature of nocturnal birds and if we were able see in the dark we would notice that their pupils are always wide open as for the adult Boobook below on the right. To me, dilated pupils look natural and can be captured by pre-focusing and turning off the focusing light a few seconds before releasing the shutter.

 

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 usually be reduced and sometimes 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 careful 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 at night, for me, present the ultimate challenge. Quality 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 and by watching with a dim red light until it flew. The Grass owl was focused in flight using a camera bracket with a high intensity focus light.

 Conclusion

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