DSLR Trailcam

After seeing high quality unique images of animals photographed using DSLR camera traps (trailcams), I became interested in the challenge of building one. The main components required are a DSLR, a sensor to activate the camera, cabling and electronic flashes. All components must be adequately shielded from the weather.

The most challenging part of the project was to obtain a low cost and reliable trigger that would activate the camera when the animal entered the frame. Most camera triggers are based on either passive infra-red motion detectors (PIR sensor) or beam sensors which use an invisible light beam to trigger the camera when the beam is interrupted. I  chose a beam sensor because they are virtually immune to false triggering and can be positioned so that the camera triggers when the animal appears at the desired location in the frame. The main disadvantage compared to a PIR sensor is that the beam sensor is an active device which requires considerable battery power and needs two modules instead of one.

I am familiar with Nikon gear which is the reason for building a Nikon trailcam but most of the information here would apply equally to other camera brands.

My main interest is in nocturnal images which is why this trailcam incorporates flash units. If you only want to capture animals during daylight you could make a simpler unit that does not require electronic flashes. You would probably set the camera to 'auto' exposure and you may wish to incorporate a circuit which deactivates the system at night.

For about a year I had fun with this setup but unfortunately it was cumbersome and time consuming to set up and I soon lost interest.

 

COMPONENTS

Camera

The camera will be left outdoors for days or weeks at a time so I purchased a cheap used Nikon D70s from Ebay. The camera must be capable of being triggered by cable which was the reason for choosing the D70s over the D70. I used a low cost  Nikkor 50mm f1.8D lens.

 

Trigger sensor modules

Commercially available break-beam sensors for wildlife photography are expensive so I decided to make one using a cheap consumer 'gate opener' and several other low cost components. The gate opener consists of an infrared transmitter and a receiver module shown below, which can operate over a distance of approximately 10 metres. They transmitter emits no visible light and when the mechanical switching relay of the receiver module is replaced the unit is totally silent.

 

 

Boost converters

Two low cost MT3608 voltage converters were used to boost the 3.7 volt output of the lithium cells to the operating voltage of the transmitter and receiver modules, which is around 10 volts.

Electronic flash

Suitable electronic  flash units must be capable of entering a low power standby mode when the system is inactive. They must also be able to be woken and fire when the IR beam is broken. The Nikon SB-800 is a high power flash that satisfies both requirements and can be  purchased cheaply second hand. One unit is sufficient for good results but a second can be used to add fill light to the harsh shadows produced by a single flash. Each SB-800 requires four AA cells which will perform for several weeks on standby and during that time can produce several hundred exposures.

 

Rechargeable Batteries

Each flash unit was powered by four 1.2 volt  'Eneloop' cells. The beam-break circuit, used seven 3.7 volt 18650 Lithium ion cells in parallel were for the transmitter and receiver modules respectively. The lithium cells could power the circuit for approximately 16 days.

 

WIRING

Transmitter

Connect as shown below. Seven 18650 cells wired in parallel  (17,500 mAh) and the entire circuit is housed in an IP67 plastic box with a transparent lid to pass the IR beam.

 

 

IR Receiver

The receiver assembly is a bit more complex but it is easy to modify with moderate soldering skill.

Step 1. Modify the receiver PCB as shown below.

 

Step 2. Wire seven 18650 cells in parallel  (17500 mAh) and adjust the output of the boost converter to 10 volts before connecting the IR receiver.

 

 

Step 3. Wire the circuit below using two "4N26" opto-coupler IC's and 500 ohm 1/4watt resistors. Connect the white and green wires from the modified IR receiver.   Connect the focus, shutter and ground outputs to a Nikon MC-DC1 remote cord as shown below. WARNING! use a genuine Nikon plug which costs a considerable amount but unlike cheap 'Ebay' knock-off plugs, it wont let you down. Originally I used a cheap plug which failed at the critical moment and prevented me from obtaining images of an Eastern quoll.

 

 

 Step 4. Protect the unit using an IP67 weather sealed housing with a transparent lid to pass the IR beam.

 

Camera to flash connections

Attach one or two Nikon flash hot shoes to a Nikon camera hot shoe according to the wiring below. Use only three wires.  Test the connections by attaching the hot shoes to the camera and flash unit(s) and set the flash units to standby mode. Power on the camera and flash units, wait for the flash(es) to enter standby mode then fully depress the camera shutter release. The flash units should awaken and fire immediately on a single actuation of the shutter release button. If they do not fire there is a problem with the wiring or connections.

 

Finished product. Weatherproof camera/flash housings not shown

 

Weatherproof housings

The IR trigger sensors , the camera, the flashes and cables must be weatherproof. The IR modules are housed in waterproof plastic boxes with transparent lids, the camera is housed in a pelican case with a 'siliconed' 90mm UV filter as the window and the flashes are mounted on poles and protected using 'ziplock' bags.

 

TYPICAL PHOTOS

These photos of a Kookaburra, Brushtail possums, Red fox and young Swamp wallaby were taken in my backyard using a single flash unit. The camera was prefocused and food was positioned beneath the beam as an attractant.

SUGGESTED SETUP AND SETTINGS

• Locate the beam across a frequently used animal trail or a location that an animal can be attracted to. Carefully select the location to ensure pleasing image composition
  
• Set camera to manual focus and manual exposure mode so you can choose the aperture and shutter speed. if desired, a low shutter speed can be used to allow ambient light to be recorded
• Pre-focus the camera on the location where the beam will be broken
• Flashes are positioned just behind and above the camera to the right and or left side to illuminate the animal at the desired angle.
• Flashes are used in manual mode with the main flash set to 1/4 or 1/2 power and the second flash to 1-2 f-stops lower.
• Select a lens aperture to give adequate depth of field in front and behind the beam and set the camera ISO for correct exposure when the main flash is set to 1/4 or 1/2 power. I do not recommend using full power settings due to long recycling times and the low number of exposures that can be obtained before the flash batteries are exhausted.
• When the setup is complete, test it by walking through the beam and checking the image.

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 are blue under UV light.  People rarely see scorpions because they are well camouflaged but where I live on the outskirts of Sydney they are quite common and are easy to find if you search the leaf litter at night using a UV light.

My initial photos were disappointing because the backgrounds looked artificially coloured. I discovered that most ultraviolet sources, also emit visible light and most cameras  record this light and also reflected UV light as unwanted colour. High output flashlights such as the ones below can be purchased online for around AU$50 (2023). They emit 365 nm ultraviolet light and include a 'ZBW' filter to block visible light. A "UV(0)" filter can also be used on the camera lens to prevent reflected UV from reaching the camera sensor and producing false colours.

 

 UV flashlights

 

 

Lichen growing on sandstone 

   

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 - Feathers of a fledgling Powerful owl and a Sulphur-crested Cockatoo - visible and UV

 

 

 Australian $5 note - visible and UV

 

Eggs - visible and UV

 

 

 Dahlia flowers - visible and UV

 

 

 

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.The additional equipment required for wildlife can be as simple as a decent camera with a focus-light and an assistant. When working with an assistant or working from your car, night photography is fairly straightforward, however when alone and outside it is beneficial to pre-configure as many camera settings as possible.

The techniques and equipment I use have evolved over many years and should be considered as a guide to be improved upon (updated 2023-12-01).

 

ILLUMINATION

Photography in darkness requires either a continuous light source or an electronic flash. There are several important differences between daylight and artificial light sources.

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 natural light photography this can be ignored because the light source is so far away from the subject that the brightness is virtually constant. With artificial illumination this is not true, as the diagram below illustrates. If the distance is doubled, the exposure needs to be four times longer or the aperture needs to be two f-stops wider.

 

 

Continuous sources such as high CRI (colour rendering index >80) flashlights, Xenon arc lamps and old-fashined halogen spotlights produce light of excellent colour quality.

Exposure is determined using the camera metering system as normal; by adjusting shutter speed, aperture and ISO. The Tawny Frogmouth below, was illuminated using the car's headlights, with camera settings of 1/15s, f5.3 and 9,000 ISO. The main disadvantages of continuous light compared to flash, is the relatively low intensity and the inability to freeze fast moving subjects.

 

 

Electronic flash is the ideal light source for freezing fast motion because it emits a short burst of intense light, however the downside compared to continuous light is that additional light is required for the camera to autofocus. Most flash units have manual settings of  full power, 1/4 power, 1/8 power, 1/16 power and 1/32 powers which is equivalent to using shutter speeds of approximately 1/250s, 1/4000s,1/8000s,1/16000s and 1/32000s respectively. This is illustrated in the image below of an operating ceiling fan photographed at shutter speeds from 1/500s to 1/4000s and flash power settings from full power to 1/32 power.

Properly exposed images can be obtained using manual power if the subject distance is known or by using 'TTL mode' (through-the-lens) as shown in the series of images below, taken at decreasing camera-subject distances.

 

In TTL mode and the camera set to front curtain sync, 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 because it is fired approximately  50 milliseconds before the main flash. Flash exposure compensation is usually necessary and at the commencement of an outing, I check my setup by taking several shots of an object such as a tree trunk, to align the flash head and to determine the amount of flash exposure compensation needed.

 

 

FOCUSING

Autofocus sensors in general adjust the focus distance to achieve maximum contrast on the image sensor. Illumination intensity, subject contrast, motion, the type of camera and the particular camera/lens combination effect the ability to focus quickly and accurately. Mirrorless cameras have auto-focus systems quite different from DSLR's and even flagship mirrorless cameras (2023) have trouble acquiring focus when a deep red focus light is used.

A small flashlight can provide sufficient light to auto-focus (AF) on stationary subjects, however flying birds require far higher brightness. The human eye is a poor judge of brightness and at night what appears bright is often too dim to focus on a flying bird.

 

GEAR

A summary of the cameras, lenses and  electronic flashes I have used is shown below.

1974-2004 (film era and manual focus equipment) Nikon F2/Nikon FM2 with 'Nikkor 300mm f4.5', 'Sunpack Auto 455' electronic flash and Kodak ISO 200 colour film.

2004-2010 Nikon D70 (6 Megapixels) with 'Nikkor 70-300 f4.5-5.6' AF lens and 'Nikon SB-800' flash. This gear was a huge improvement on manual focus cameras and film.

2010-2012 Nikon D90 (12 Megapixels) with 'Nikkor 70-300 VR', 'Nikkor 80-400 VR' and  'Nikon SB-800' 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.

2022-2024 Nikon Z6ii (24 megapixels), Nikon Z8 & Nikon D850 (45 megapixels)  with 'Nikkor 100-400mm zoom,  300mm and 500mm primes and Nikon SB-800 flash. Mirrorless cameras are a joy to use at night because the viewfinder can  see clearly in almost total darkness. For birds flying at night I use the D850 with 300mm f4 lens in conjunction with a  deep red (660nm) red light.

 

Flash extender - consists of a Fresnel lens placed in front of the flash window, which concentrates the light output. It produces a 'hotspot' with a 3-4 f-stop gain in brightness and is very useful in conjunction with a telephoto lens. 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 works well but I have found flying birds often try to evade a bright white light, making it difficult to focus. Red light (660nm) with DSLR PDAF autofocus works very well  and induces minimal evasive response. Green light (550nm) is ideal for focusing mirrorless cameras on stationary subjects but works poorly on flying birds which try desperately to evade it. Coloured lights are problematic in that a strong colour cast, which  can be difficult to remove in post processing, is often present in the shadows of the image. To minimise this problem I use the circuit below to turn the focus light off for approximately 1/20s the instant that the flash fires.

The benefit of the circuit can be seen by comparing the two images below which were taken using the same exposure (f5.6 1/90s ISO 2200). For the image on the left the momentary circuit prevented most of the green light from appearing in the final image. The right-side image was taken with the circuit disabled.

 

 

  

Flash brackets can be used to minimise 'Red-eye'. A home-made carbon fibre bracket and a green focus light incorporating the 'momentary circuit', is shown below. 

 

 

Tripods are useful when slow shutter speeds are required at fixed locations such as perches, roosts or nests. A lightweight tripod can support the camera or be used as a stand for an off-camera flash.

 

Off-camera flash - I use 'Pocket Wizzard' radio triggers to fire flashes located off-camera. Other systems such as Nikon's 'CLS' system or sync. cables  are less reliable and time-consuming to set up.

 

CAMERA SETTINGS

Settings Banks - Many cameras allow you to save your favourite settings for quick recall, which is very useful at night.

Image file format - RAW files have higher dynamic range and great capacity for salvaging images taken with non-optimal camera settings.

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

Shooting Mode - I use manual camera settings and either TTL or manual flash power settings.

Focus - For stationary birds I use the centre autofocus point with the camera set for 'back-button 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. Today's cameras have countless autofocus modes which need to be explored to discover which work the best.

ISO - Producing sufficient light for correct exposure or to obtain motion-free images can sometimes 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 generally 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 reduce the aperture by half an f-stop to minimise the affects of any auto-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 freezes motion.

For stationary subjects, low shutter speeds can be useful for recording ambient light. The Barking owl below remained sharp because it was exposed by the pulse of light from the flash, whilst the background and twilight was revealed using a long 1/15 second exposure.

 

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

 

 

 

NOCTURNAL EYES

Pupils - A bright continuous light source produces contracted pupils when the bird is looking directly at it (or you). This is especially noticeable for a bird with a pale iris such as the young Boobook 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 in the dark. I consider dilated pupils to look natural  and they can be captured by pre-focusing the camera then turning off the focus light just before releasing the shutter (right-side image below). When focus is achieved and before the shutter is released, the subject can be observed through the viewfinder using a very 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 further away from the camera or moving closer to the subject, the likelihood  of red-eye 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 try 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 the internal structures of the eye.

 

 

FLYING BIRDS

A sharp image of birds flying at night is probably the ultimate challenge. A sharp image 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 hunting from and watching it with dim light until it flew. The Grass owl was focused in flight using a high intensity focus light.

 

 

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 eyes 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. 

In most vertebrates, rod cells which have a peak spectral sensitivity at approximately 500nm (dotted curve in graph below) are completely insensitive to red light. Consequently, you can observe many nocturnal species at night by using dim red light without causing 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 contain red sensitive L-cones.

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..

 Human perception of colour under widely different levels of illumination is summarised below. 

 

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 colours of objects illuminated by starlight or the partial 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.

 

 

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 shades of grey or blue as depicted in cinema movies. Moonlit 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

   

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 combined signals from the different cone types, analogous to mixing the primary colours to achieve 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.

 

 

ILLUMINATION

High intensity flashlights are great for finding animals at night but are not well 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. 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 another species. Playing of calls is often used in owl surveys, by bird watchers (twitchers) and photographers. When searching for owls at new locations, I often use recordings of their calls. Call playback can be highly disruptive if not used judiciously and I do not encourage indiscriminate usage. Playing calls 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 to walk on 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, insect 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.