Thermal or night vision: a buying guide

Thermal and night vision solve two different problems. A thermal device shows you radiated heat, and with it finds what you would otherwise never notice at all. A night vision device amplifies the light that is already there and shows you what the thing you found actually is. Heat detects, available light identifies.

So the common question "thermal or night vision" is almost always the wrong question. Our own devices do not answer it with an either/or: the DTD Jerry C5 and the Jerry-C PRO are thermal fusion for night vision, front attachments that lay a thermal channel over the intensified image instead of replacing it. This buying guide explains when that is the right answer, and when a better tube would be.

What the tube sees, and what the sensor sees

An image intensifier works with photons that are already there: starlight, moonlight, the spill from a village on the horizon. It amplifies them and returns a picture that shows the scene roughly as your eye would see it by day. Shapes, surfaces, edges, writing, depth in the terrain. That is enough to walk, drive, read and tell a target from a non-target.

A thermal sensor works with radiation the object emits itself. It needs no light at all, none, and it shows temperature differences instead of brightness differences. A deer in the shadow of a hedge, a person behind vegetation, an engine that was still running twenty minutes ago: all of it stands out against the colder background, however dark it is. Cover that stops light does not necessarily stop heat.

The price of that is detail. On a thermal image a person is a bright patch in the shape of a person. That somebody is standing there, you see at once. Whether they are carrying a rifle or a spade, and whether they are your neighbour, only the tube tells you. Both devices see in the dark. They simply do not see the same thing.

Detection, recognition, identification

A listing usually carries a single range figure. It is almost always the detection range, which is the largest of the three numbers you actually need.

• Detection: there is something warm, roughly this big.
• Recognition: it is a person, a deer, a vehicle.
• Identification: it is that person, that animal, that object in the hand.

The gap between the stages is large, and you can read it off our own published figures. The DTD Jerry-C PRO COTI Thermal Fusion states detection up to 1000 m and recognition at 275 m. Between "there is something" and "it is a person" sits a factor of well over three. Identification is closer again, by a wide margin.

Read a range figure while thinking about identification and you are out by a multiple. That is also the argument for fusion: the last stage is the tube’s job.

What fusion means, and why a front attachment is not a monocular

A standalone thermal monocular gives you the thermal channel on its own. You find the warm body and, in the same moment, lose everything the tube was telling you about the surroundings. To work out what you have found you swap devices, lose seconds, lose your line of sight and, depending on the scene, some of your dark adaptation. Those are exactly the seconds in which the thing you found moves.

A front attachment takes that swap away. The thermal channel sits over the intensified image, in the same eyepiece, at the same moment. You keep the tube’s detail and get the heat cue on top of it, not instead of it. If you move between searching and recognising under time pressure, that is the thing you are buying.

In practice, across our two units: the DTD Jerry C5 COTI Thermal Fusion carries a 640 x 512 sensor, a 30.5 degree field of view at 1x magnification, an aluminium housing at 110 g and IP67, and mounts to fielded night vision devices without modification. The Jerry-C PRO has a 35 degree field of view, the same sensor in 12 micron, cleaner image processing, a built-in digital compass, controls you can work with gloves on and remote operation, at approximately 115 g, and sits on PVS-14 pattern optics via an adjustable ring clamp.

Plan for runtimes in hours, not in nights: the PRO states about 3 hours on a CR123A and up to 10 hours on the external battery pack. A second device on your head is also a second battery level to watch. Send us your device model before you order and we will confirm the fit.

When you actually need thermal

The useful question before buying is not "heat or light", it is this: what is failing on your night as it stands?

• The image is there, but noisy, hazy or too short. That is a tube problem, not a heat problem. The answer is a better signal to noise ratio, not a sensor. Why the big number on the product page does not answer it is set out in what figure of merit does and does not tell you.
• The image is good, but you find nothing. Searching open ground, thick undergrowth, deep shadow, new moon. That is thermal’s job, and here it beats the tube outright.
• You need to tell things apart, not find them. Tube. Always.
• Both, in the same night, without swapping devices. Fusion.

One point sales conversations tend to leave out: a thermal device is a poor navigation instrument. It flattens the terrain, and water, wire fences and trip hazards are effectively invisible. Walk unfamiliar ground on thermal alone and you will notice inside two hundred metres. If you want to move in the dark you need a tube first: it makes sense to buy a night vision device before the thermal channel, not after it.

The honest limits

Glass. Behind a window pane, thermal shows you nothing. Window glass and car windows are opaque at that long wavelength, so you see the pane and not the room behind it. The tube looks through the same window without difficulty as soon as there is any light inside.

Weather. Rain, fog and high humidity cost range, and they cost a thermal sensor considerably more than they cost an image intensifier.

Thermal crossover. At dusk, and shortly after rain, target and background even out in temperature. The contrast collapses, and a device that showed every animal in the field an hour earlier shows a grey surface. That is not a fault, and it is on no datasheet.

No identification. You do not identify on a thermal image. If you have to positively identify something, you do it through the tube and with your own eyes, never off a warm silhouette.

Cost and bulk. A front attachment is a second device: a second purchase price, a second battery, extra weight on a head that already carries one. Current prices are on the product pages, not in this text.

Hunting, weapons and the law in Switzerland

In Switzerland, buying and owning an observation device is treated differently from an aiming device fitted to a weapon. And the decisive point for thermal: a device is not treated differently because it images heat rather than available light. What governs is what it is used for. A thermal device used to aim is an aiming device.

Three enactments touch the subject, and they govern three different things. The Waffengesetz, the Weapons Act (WG, SR 514.54), lists night vision aiming devices as prohibited weapons accessories; exceptional authorisations are decided by the competent cantonal authority. The Jagdverordnung, the Hunting Ordinance (JSV, SR 922.01), separately governs which aids are permitted when hunting; hunting is administered by the cantons, and what applies in your canton is a question for the cantonal hunting authority. The Güterkontrollverordnung, the Goods Control Ordinance (GKV, SR 946.202.1), concerns neither possession nor use, but export.

This is a summary of the statutory position and not legal advice. The binding decision rests with the competent cantonal authority, and it is a question you ask before buying, not after. There is more detail in night vision and Swiss law.

Delivery, export and trying one

Thermal devices, like night vision devices, are controlled goods. We deliver to Switzerland, Liechtenstein and the EU and Schengen countries, and nowhere else. Every delivery outside Switzerland and Liechtenstein requires a signed End User Certificate: after payment we send you the certificate, you sign and return it, we complete Swiss export clearance, and the device is dispatched to you with tracking. If clearance cannot be obtained for your country, the order is refunded in full. Russia, Belarus and sanctioned jurisdictions are permanently excluded.

Both units carry the two-year DTD warranty. And the only test that has never lied to anybody is still looking through the thing: in the dark room in Villmergen, by appointment, the same tube once with and once without the thermal channel.

The short version

• Thermal sees heat and finds. Night vision sees light and recognises. Two jobs, not two price brackets.
• The range quoted is the detection range. Recognition is a fraction of it, identification closer still.
• Fusion means a thermal channel over the intensified image, no swapping devices, no loss of detail.
• A noisy or hazy image is a tube problem. No sensor fixes it.
• Glass, rain and thermal crossover are real limits, not excuses.
• In law, aiming is not the same as observing. Ask your canton before you buy.

Questions at any level of detail are welcome, including on fit to a device you already own. info@dtdsystems.ch, +41 76 225 50 04. The full range: all DTD night vision and thermal devices.

The matching devices are in the range: buy thermal fusion in Switzerland.