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Ultraviolet Fluorescence

Ultraviolet light (UV) is invisible to the human eye but when certain substances are exposed to it, they emit visible light. I became interested in photographing fluorescence when a friend told me that scorpions appear blue under UV.  People rarely see scorpions because they are brown and well camouflaged but they are quite common where I live on the outskirts of Sydney and are easy to find at night by searching the leaf litter with a UV lamp.

My initial photos were disappointing because the backgrounds looked artificially coloured. I discovered that most ultraviolet sources, also emit visible light and cameras often show this visible light and reflected UV as unwanted colour. I built the lamp below to prevent false colours and I also use a "UV(0)" filter on the camera lens to prevent reflected UV light from reaching the camera sensor. My UV lamp and a selection of images exposed using UV and visible light are shown.

The lamp was built for less than AUD $100 and includes:

  • 10 watt 365nm UV LED
  • A black  "ZWB2" filter inserted beneath the LED and lens to block unwanted visible light emitted by the LED
  • Condenser lens on the front of the lamp to concentrate the UV into an intense beam which makes the fluorescence look more vibrant and reduces exposure time
  • Resistor and heatsink to prevent the LED overheating and to limit the maximum current
  • Rechargeable 3.6 volt lithium cell

 UV lamp

  

Diamonds - visible and UV light

 

Marbled Scorpion - UV exposure for 6 seconds at f16 and fill flash. Nikon D750, 180mm lens with UV0 filter, extension tube and tripod

 

Feathers - Fledgling Powerful owl feather and aSulphur-crested Cockatoo feather exposed with visible and UV  light

 

 

 Australian $5 note - visible and UV light

 

Eggs - visible and UV light

 

Lichen growing on sandstone - visible and UV light

 

 

 

 

Night photography

I have enjoyed photographing night creatures for nearly 40 years. With the advancement in camera technology and lighting it is now possible to photograph birds flying at night. and my . The additional equipment required for wildlife can be as simple as a decent camera with good focus-light and an assistant. When working with an assistant or working from your car, photography at night is fairly straightforward, however when alone I find it beneficial to pre-configure as many settings as possible before nightfall.

My techniques and equipment described below have evolved over this time and should be considered as a guide which can be improved upon (updated 2023-01-16).

 

ILLUMINATION

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

A fundamental of light is that the brightness of an illuminated object, decreases in proportion to the square of the distance from the light source. For photography in natural light, this can be ignored because the relative distance from the light source only changes by an infintesimal amount. When illuminated with artificial light this is not true, as the diagram below illustrates. If the distance is doubled, the exposure needs to be four times longer or two f-stops wider. If the distance is halved, the exposure needs to be reduced by the equivalent of two f-stops.

 

 

Continuous light sources such as spotlights are great for photographing stationary or slow moving animals. Filament lamps and Xenon arc lamps produce light having excellent colour quality but are heavy on battery power. LED lights are portable, bright and energy efficient and those having a high colour rendering Index (CRI greater >80) produce excellent colour rendition.

Exposure is determined with camera metering system by adjusting shutter speed, aperture and ISO. The Tawny Frogmouth below, was illuminated using the car high beam, with camera settings of 1/15s, f5.3 and 9,000 ISO. The main disadvantages of continuous lighting is the relatively low light intensity and the inability to freeze motion.

 

 

Electronic flash is the ideal portable light source because it emits a super intense burst of high colour quality light which can freeze motion, however an additional light is required to enable the camera to autofocus in darkness. Flash units contain complex electronics that produce an electrical discharge inside a transparent tube and when sufficient light has been emitted, the discharge is terminated. Most models have auto and manual modes which can be configured to produce the correct exposure. A typical high power electronic flash (Nikon SB-800); on full power, 1/4 power, 1/8 power, 1/16 power is equivalent to using a shutter speed of approximately 1/250s, /4000s,1/8000s,1/16000s and 1/32000s respectively. This is illustrated in the image below of a ceiling fan photographed at different shutter speeds from 1/500s to 1/4000s and flash power settings from full power to 1/32 power.

 Advanced electronic flash units have automatic and manual power modes. Properly exposed images can be obtained using manual power if the subject distance can be estimated. Well exposed images can be obtained using 'TTL mode' (through-the-lens) without any knowledge of the subject distance as illustrated in the series of full-frame images below, taken at decreasing camera-subject distances with the flash exposure compensation set to minus 1, f-stops.

 

In TTL mode with the camera set to front curtain sync, illustrated below, a pre-flash is fired just before the camera shutter opens, which allows the camera to calculate the amount of power needed for correct exposure. The pre-flash cannot be seen by eye because the interval before main flash is of the order of 50 milliseconds. Some flash exposure compensation is usually necessary and at the commencement of an outing, I check my setup by taking several test shots of an object such as a tree trunk, to ensure correct alignment of the flash head and the amount of flash exposure compensation required.


 

 

FOCUSING

Autofocus sensors in DSLR and mirrorless cameras essentially adjust the focus distance to achieve maximum contrast on the image sensor. Illumination intensity, subject contrast, motion, and the particular camera/lens combination effect the ability of a camera to focus quickly and accurately. Mirrorless cameras have different autofocus systems compared to DSLR's and even flagship mirrorless cameras such as the Nikon Z9, are not on par with high-end DSLR's when red-light is used for focusing.

A small flashlight can often provide sufficient light for auto-focus (AF) to work on stationary subjects, however flying birds require far higher brightness. The human eye is a poor judge of brightness and at night what may appear bright to the photographer is often insufficiently intense for the camera to autofocus on flying birds.

 

GEAR

Cameras, lenses and flashes - A summary of the gear I have used for wildlife night photography is shown below.

1974-2004 (my 35mm film days using manual focus lenses) Nikon F2/Nikon FM2 with 'Nikkor 300mm f4.5' and  'Sunpack Auto 455' electronic flash

2004-2010 Nikon D70 (6 Megapixels) with 'Nikkor 70-300 f4.5-5.6' AF lens and 'Nikon SB-800' flash. My first DSLR and autofocus camera was a major improvement on manual focus and film

2010-2012 Nikon D90 (12 Megapixels) with 'Nikkor 70-300 VR', 'Nikkor 80-400 VR' and  'Nikon SB-80'0 flash.

2012-2015 Nikon D7000 (16 megapixels) with 'Nikkor 70-300 VR AFS', 'Nikkor 80-400 AFS VR' and 'Nikon SB-800' flash. Better autofocusing enabled photography of birds flying at night

2015-2021 Nikon D750 (24 megapixels) with 'Nikkor 180mm f2.8', 'Nikkor 80-400 AFS VR' and 'Nikon SB-800' flash. 24 megapixel full frame camera produced fantastic image quality and better results all round

2022 Nikon Z6ii (24 megapixels) & Nikon D850 (45 megapixels)  with 'Nikon 300mm f4 PF', 'Nikkor 500mm f5.6 PF' and Nikon SB-800 flash - Better image quality than the D750 and the electronic viewfinder of the Z6ii is a joy because it can be be configured to see clearly in almost total darkness. I use the D850 with 300mm f4 lens for night photography using a 660nm red focus light.

 

Flash extender - consists of a Fresnel lens placed in front of the flash window, which concentrates the light output over a small area. It produces a 'hotspot' with a 3-4 f-stop gain in brightness and is very useful for night photography using a telephoto lens. To demonstate how it works, the images below were taken with a 50mm lens using identical exposure and processing, without and with a flash extender.

 

Focus lights A white focus light can work well but I have found that flying birds often veer away from the light making it difficult to nail the shot. Red light (660nm) is ideal for DSLR cameras because it works well and induces minimal evasive action from the flying bird and green light (550nm) works well for my Z6ii Mirrorless camera when photographing stationary animals. Coloured focus lights are problematic in that a colour cast can result in the final image which is difficult to remove in post-processing. To address the problem I developed the circuit below, which turns the focus light off for approximately 1/20s each time the flash fires. 

 To show the benefit of the circuit the images below were taken using the same ISO, shutter speed and aperture, except the flash was turned off for the image on the right.

 

A selection of red and green focus lights incorporating the circuit is shown.

 

 

Flash brackets can be used to minimise 'Red-eye'. As selection of DIY carbon fibre brackets incorporating focus lamps are shown below


 

Tripods are useful at night at fixed locations such as perches, roosts or nests or during the day for dimly lit locations that require slow shutter speeds or hand holding for extended periods. A portable lightweight tripod can be used to support the camera or as a stand for an off-camera flash.

 

Off-camera flash - Occasionally I use radio triggers to fire flashes located away from the camera. Previously, I used Nikon's 'CLS' system and sync. cables but found them to be unreliable and time-consuming to set up.

 

CAMERA SETTINGS

 Settings Banks - Many cameras allow you to save your favourite settings for quick recall, which is a very useful in the dark.

 Image file format - RAW files have high dynamic range and the capacity for salvaging images which have been over or under exposed and to set the white balance post-exposure.

 LCD Monitor/viewfinder - Display monitors appear much brighter in the dark and images which appear adequately exposed are often significantly underexposed. To counteract this, I turn the monitor brightness down and regularly check the image histogram.

 Shooting Mode - I use either TTL or manual modes.

 Focus - For stationary birds I use the centre autofocus point with the camera set for 'backbutton and continuous autofocus' which makes it easy to recompose the image without having to refocus. For flying birds, continuous AF and multiple focus points works well. Modern DSLR's and Mirrorless cameras have many autofocus modes which need to be explored to find which ones work best.

 ISO - Producing sufficient light for correct exposure or to obtain motion-free images can be difficult. Using a higher ISO is equivalent to using a more powerful flash, however this produces more image noise. On my current cameras ISO 800-1600 produces 'acceptable' results.

 Aperture - A wide aperture is desirable to isolate the subject from the background and to increase the maximum working range of the flash, however, I usually stop the lens down slightly from the maximum aperture to minimise the affects of AF focus errors.

 Shutter speed - The shutter speed should generally be set to the maximum flash sync speed which for most cameras is around 1/200s. In darkness fast shutter speed is irrelevant because it is the short duration of the flash output which exposes the image and freezes motion.

For stationary subjects, a low shutter speed can be useful to record ambient light. The Barking owl below remained sharp because it was exposed by the short pulse of light from the flash, whilst the ambient light is revealed. The foreground branch shows blur from camera movement associated with hand-holding at 1/15s exposure.

 

For flying birds, low shutter speed combined with 'rear-curtain sync.' can be used to produce light trails, giving the illusion of speed, as for the Nightjar below, taken with a 1/30s exposure. Often however, a potentially good image, such as the Grass owl with prey, shown in the second image are ruined by the excessive blur.

 

 

 

NOCTURNAL EYES

Pupils - A continuous white light source always produces contracted pupils when the bird is looking toward it. This is especially noticeable for a bird with pale irises such as the young Boobook owl in  the left side image below. Large eyes are a prominent feature of nocturnal birds and if we could see in the dark we would notice their pupils are always wide open. I consider dilated pupils look more natural  and they can be captured by pre-focusing the camera then turning the focus light off for a few seconds before releasing the shutter (right-side image below). After focus is achieved and before the shutter is released, the subject can be observed through the viewfinder using an extremely dim 'moon-glow' light.

 

Red-eye occurs when the light source is located 'close' to the camera and light reflected from the retina enters the camera lens. By moving the light source away from the camera or moving closer to the subject, the likelihood  of red-eye in your photos can be significantly reduced. This is illustrated in the diagram and images of a Tasmanian Boobook owl below.


 

Red-eye correction -  Sometimes you cannot avoid red-eye as seen in the left and centre images above, however usually it can be 'fixed' with good 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 below. In close proximity to an owl at night, a single light source often produces multiple catchlights due to reflections from the cornea and eye lens.

 

 

FLYING BIRDS

Sharp images of a birds flying at night 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 phoyographed by pre-focusing on the perch it was hunting from and watching with a dim red light until it flew. The Grass owl was focused in flight using a high intensity light source.

 

 

Observation at Night

Night observation is very different from observation during daylight. At night we rely on our senses of hearing and sight in conjunction with artificial light to locate  an animal. Nocturnal animals have very acute senses compared to ours and they are usually aware of our presence long before we detect them. Often I find an animal by its call or noise, then locate it by it's eye-shine.

 

VISION

Vision is a complex sense which involves the brain interpreting signals from the light sensitive rod and cone cells in the retina at the back of the eye. Cones are fully active in bright light and rods only work in very dim light. Diurnal animals including humans have cone dominated vision which enables excellent colour perception in daylight with high visual acuity. Nocturnal species have eyes with a greater proportion of rods, which makes for enhanced vision in low light. Nocturnal predators also have a number of physical adaptations to collect more light, including larger eyes having a short focal length, wide aperture and often a highly reflective tapetum lucidium which allows light to pass twice through the retina.

 

Daylight vision  (Photopic vision) - The eye contains several cone types, each having a peak sensitivity to a different light wavelength. The brain 'sees' colour; not the eyes and it does so by interpreting the signal from each cone type, analogous to mixing the primary colours to achieve all the colours of the rainbow. In bright light it is generally believed that the more cone types a species has, the better is its ability to distinguish colours. Mammals have either two or three cone types whilst birds, reptiles and fish have at least four, which probably enables superior colour perception and the ability to see into the ultraviolet part of the spectrum.

The graph below shows the spectral sensitivity of the rods and cones in the human eye. The cones types are referred to  as 'L', 'M, and 'S' , referring to long, medium, and short wavelengths, respectively.

 

 

Night-time vision (Scotopic vision) - In very dim light cone cells don't function and the brain processes the signals it receives from the rod cells. As there is only one type of rod cell, the brain cannot use the rods to perceive colour, which is the reason why we can't see the true colours of objects illuminated by starlight or the moon.The image below  of children's crayons  photographed in starlight (15 seconds, f1.8, ISO 9000), shows that unlike us, the digital camera sees colour perfectly even when we perceive only shades of grey.

 

In the majority of vertebrates, rod cells which have a peak spectral sensitivity at approximately 500nm (dotted curve in graph above) are completely insensitive to red light. Consequently, you can often observe nocturnal species illuminated using dim red light without any visual disturbance. Different species see red light to varying degrees and nearly all can see a red light if they look at it because their retinas do containsome red sensitive L-cones.

 

Twilight vision (Mesopic vision) - Twilight is the period between night and day when the sun is below the horizon and during this time both the rods and cones are active. Colours appear muted compared to the colours we see during the day. If you sit in your garden after sunset you will notice, the colours around you start to disappear as the cones slowly switch off. The longer wavelengths such as red disappear faster than the shorter wavelengths and this is known as the 'Purkinje effect'.

The fact that the brain interprets the signals from our eyes and sees colour can result in optical illusions and incorrect colour perception. Moonlight is reflected sunlight having a colour temperature of approximately 4000K, yet our eyes perceive only shades of grey or blue as depicted in cinema movies. Night scenes photographed with a digital camera with a white-balance set to daylight, show a full range of colour with a strong yellow cast. 

 

ILLUMINATION

High intensity flashlights are great for finding animals at night but are not suited for studying their behaviour. White light has the advantage that you can see the true colours including the colour of an animal's eye-shine, which can be useful for rapid identification. The photo below shows the distinctive blue eye-shine of a Mouse deer in my hotel grounds in Sabah, Borneo.

 

Bright white light directed into the eyes of an animal may cause temporary night blindness lasting at least 10 minutes, during which time the animal could become susceptible to predation or injury. Rods don't see red, which suggests that rod dominated nocturnal eyes have poor sensitivity to red light. Consequently red lights such as my headlamp below are ideal for observing the behaviour of nocturnal animals. This headlamp can be attached to a tripod and the beam angle can be adjusted to control the brightness. The main disadvantage in using a red light is that true colours cannot be discerned.

 

 

The photo below of a Powerful owl bringing a freshly killed Ringtail possum to it's nest was taken using the headlamp above (1/3 second exposure, f6.3, ISO 6400). I observed this nest for many years using red light and the owls were always aware of my presence but were unconcerned. If a white light was used I may not have been able to observe their behaviour and in the worst case, the owls may have abandoned their nest.

 

 

 

ATTRACTION AIDS

Many birds and mammals can be attracted by playing their calls and sometimes by playing the call of other species. Playing of calls are often used in owl surveys, by bird watchers (twitchers) and photographers When searching for owls at new locations, I use playback of their calls. Call playback can be highly disruptive when not used judiciously and I do not encourage it's indiscriminate usage. Playback near nest sites during the breeding season is strongly discouraged. You should resist the temptation of divulging owl locations to photographers and twitchers because owls are strongly territorial and are vulnerable to disturbance.

 

WALKING at NIGHT

Long-sleeved shirt, long pants and sturdy boots afford protection from cuts, scratches and bites. I prefer walking along well defined tracks because you can move quietly and are likely to see more animals. Depending on the weather and location, I may take extra clothing, bug repellent and something to sit on. Being alone can be very rewarding and you usually see more animals because your senses are heightened, however you need to be more careful. At night your vision and sense of direction is impaired and it is easy to become disoriented and trip on something you didn't see. Before I venture alone I familiarise my route and tell someone where I am going.

 

Richard Jackson

 

 

As a child I grew up in the northern suburbs of Sydney with Ku-ring-gai Chase National Park as my back yard. After school and on weekends I would spend countless hours with my best friend and school mates exploring the bush, catching tadpoles, yabbies and cicadas, damming creeks and playing hide and seek.

 

During those years I developed a love for the bush and became interested in the various birds and mammals that lived around me. I was always fascinated by the wonderful wildlife photos in National Geographic magazine and was in awe of the SLR film cameras advertised on the back page. My passion for nature photography started at age fourteen when my parents bought me my first camera, a Kodak Instamatic. Dreams of magazine images were shattered when my first roll of film was developed and the beautiful Robin in my mother's rose garden appeared as a scarlet speck.

 

By age seventeen I had saved enough money for a Nikon F2 SLR camera and 300mm lens which my father purchased, duty-free. Without success in achieving the stunning images I dreamed of, my interest in wildlife photography waned until after my first child was born. It was then when free time was scarce, I decided one night to venture into the Royal National Park, near my home in Engadine, to see if there were any animals about. To my surprise and delight I saw possums and watched a Tawny Frogmouth fly to a dead limb, close enough for me to photograph.

 

After overcoming my fear of the dark I quickly started enjoying the solitude of being alone in a world of nocturnal creatures and the uncertainty and excitement of what I may find. With the advent of affordable digital cameras with fast and accurate autofocus and bright LED lights, it became much easier to take quality images at night. I now look at my prized film photos from the past and keep them as momentos.

 

Until recently, my main photographic interest has been owls and nocturnal mammals and recently my interests have widened to include other subjects. I love nothing more than heading into the bush when most people are calling it a day. As the sun sets a world few are aware of awakens, where I observe creatures and sights that most only see in books.

 

I owe my continued interest in this hobby to Julie my wife for her loving support and ongoing encouragement for over thirty years. A big thank you to Gerard Satherly who built this website for me and to the friends I have made at Feathers & Photos forum who have taught me so much about bird photography and digital processing.

 

You are welcome to use my images and articles for your personal not-for-profit use, such as projects etc, but please reference me as the source. All of my images and articles are copyright so if you would like to use them for another purpose please contact me before doing so. My e-mail address is prsj56[at]optusnet.com.au