Thermal head-to-head

Simon Barr has a heated debate over two leading thermal imaging units currently on the market and available to night shooters

The competitor: The Guide is the newer addition to the UK market

We are at the dawn of a new era for wildlife management. Thermal imaging technology is by no means new, but with two companies launching units for the consumer market at affordable (relatively speaking) price points, this technology is no longer for the exclusive use of the police and military.

Many will be aware of night vision technology, which uses either a digital or vacuum-tube based device to convert dim light from the visible and infrared spectrum to an image in a device that can be viewed by the naked eye. Most commercially available night vision units rely on an active infra-red light source, which is visible to wildlife. Animals can see much further into the infrared spectrum than we can. You will have witnessed this if you have ever seen a dog running through woodland at night avoiding trees and eye-height obstacles.

Thermal imaging technology detects thermal radiation, and requires no additional source of illumination whatsoever. All living beings, particularly warm-blooded ones, have heat signatures. Inert objects such as stones, roads and buildings also have heat signatures as they absorb heat during the day from the sun’s radiation. Thermal imaging technology exaggerates small temperature differences and displays these in a way that can be viewed on an LCD screen. This is typically in greyscale, with the hot areas either white hot or in negative. There is crude detail, and often you just have outlines to identify objects by. It is remarkable to see how well insulated a fox is, for example – the tips of its ears are the only truly white hot areas on its body.

Double vision: Two thermal imagers go up against each other in a test of new technology

Earlier in the summer I reviewed the USA-made FLIR Scout TS32 Pro. To my mind the FLIR was a good start at consumer thermal imagers, but still needed a lot of development to make it truly usable in the field. There were some design flaws on the unit, which restricted how well it would perform in real-life scenarios. I was therefore interested when Thomas Jacks took delivery of a new thermal imager unit from Chinese manufacturer Guide IR. In a similar vein to the FLIR, the Guide IR units have been designed for hunters, wildlife enthusiasts and security uses.

I was sent a Guide IR 518C to test. This is the top-of-the-range unit, retailing at £4,849.95 – not quite within the grasp of the average stalker, but certainly affordable for an estate or professional deer manager as a tool of the trade. The FLIR unit I had reviewed was £5,439.99 – almost £600 more expensive. With a total of eight units in the FLIR range, the units I had for review seemed a fair comparison based on price.

The Guide unit initially felt slightly less ergonomic to hold than the FLIR, but this might be a subjective, personal view. The Guide IR has an exterior rubber housing that sleeves the body and overall has a typically utilitarian feel to it. There was no quality issue with the Guide IR, but the FLIR felt marginally better in my hands. I doubt this would really matter to any user when out surveying wildlife or selecting specific animals to cull.

The first major difference that I noticed was the large lens on the front of the Guide IR unit – all 50mm of it. There are three models in the Guide IR range: models A and B, which have 25mm lenses, and the C, which has a 50mm lens. The entire FLIR range has a 19mm lens, which offers far shorter detection ranges. The FLIR Scout I reviewed can recognise a man-sized object at 200 metres whereas the Guide IR can detect the same at 500 metres. This is certainly because of the size of the lens.

The Guide also excels in field of view. The field of view is decided by the image resolution and number of pixels the sensors deliver. The FLIR offers 320×240 and the Guide IR brings 384×288 – these extra pixels can be incredibly useful in the field where fast detection might be necessary.

A key point when I reviewed the FLIR was how inaccessible the battery compartment is. The literature that comes with the FLIR claims five hours’ usage from one set of batteries, but I struggled to get an hour’s use out of the unit. To change the batteries in the field, you need a tiny watchmaker-type screwdriver to unscrew four small screws on the battery compartment on the bottom of the unit. Not a practical solution at night in the rain with cold hands. Changing the four AA batteries on the Guide IR is simple, as it should be on a power-thirsty piece of kit such as this. The Guide IR promises two hours’ usage, and I was keen to see how honest this would turn out to be when I used it.

Fully focusable: The Guide’s bigger, adjustable lens proved a point in its favour

When you switch the Guide IR on, it takes about 25 seconds to go from the off setting to on. The FLIR takes around 90 seconds to do the same thing. Once the Guide IR is on, the clarity is significantly sharper than the FLIR. The screen refresh rate is at 50hz, which is the same as many televisions. This gives you a real-time picture with no lagging when you scan with the unit. The FLIR has a frame rate of 8hz, meaning the images drag behind your movements when scanning. This could lead you to lose detail when looking at a dynamic object like a living animal.

A clever design feature on the Guide IR is the sensor on the back of the unit next to the eyepiece, which keeps the unit on when you have it up to your eye and automatically puts it on standby when you bring it down. This is a good way of regulating battery usage, and it stops excessive light spilling out of the unit when it is not up to your eye.

The FLIR’s 19mm lens has a fixed focal length, but it claims all objects will be in full focus. However, you simply cannot have everything in pin-sharp detail with a fixed focal lens. The Guide IR’s 50mm lens is fully focusable, which takes a while to get used to. Once I had mastered its operation, I was able to focus on a squirrel in a tree 180 metres away, as ranged with my binos.

Both units boast a digital 2x zoom capability, which is useful – but both units could do with a bit more zoom. Every Guide IR model comes ready to take videos and capture images, whereas this is only available in the higher FLIR models.

In the field on a cold night, the Guide IR certainly did the business. I was amazed at the level of detail I could see. The image was crisp and in complete real time. I used a rangefinder to see to what distances I could detect animals, and I found that deer were easy to spot at up to 1,000 metres.

It took a few hours to get used to what size different heat signatures looked like. Rabbits initially looked like boar and deer like horses, but I soon got the hang of it. For animal census surveys, this tool would be very useful. The battery life lived up to its two-hour promise, and I was able to change the batteries with ease when they did run down. This was still a nuisance, as you’d need three or four changes of batteries to spend a full night out in the field, but a little forethought and planning can overcome that. The ultimate set-up for wildlife management would be to use thermal imaging for detection and then night vision to positively identify what you are looking at – if money was no object, of course.

The FLIR Scout I reviewed costs £5,439.99. There is an entry model at £2,999.99 and another seven models ranging up to £7,499.99. The entry model A on the Guide IR range is at £3,099.95, and the top-of-the-range model C is £4,849.95. Although it is £600 cheaper than the FLIR I tested, it is a far more powerful proposition.

Thermal imaging will undoubtedly make a big difference to wildlife management across the UK. The technology is cutting-edge and the applications are endless. As far as these two units go, beauty is inside the eye of the holder. Although the Guide IR might not have the aesthetic appeal of the FLIR Scout, having spent many hours looking through the eyepieces of both, I know which I would buy.

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Posted in Features, Optics, Reviews
One comment on “Thermal head-to-head
  1. Interesting article. It would be really great to see you test the new Pulsar Quantum HD38. I’ve had one for 2 months now, and am extremely impressed with it.

    Ant

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