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In an attempt to demystify thermal imaging and night vision systems in practical terms, it is hoped these notes might go some way in helping to overcome those "dark" secrets and misinformation that continues to surround them.
The following pages are long, and may be considered boring to a casual reader, although may possibly contain some specific information that could be of interest to a serious reader.
YOU HAVE BEEN WARNED !
The following sections discuss
Thermal Imaging or Image Intensifying -
Facts about thermal -
Using night vision -
Considerations for a night vision scope -
What you will see? -
Workshops on all types of night vision and thermal imaging can be arranged at no cost.
(Depending on location).
Covering a discussion session and then the opportunity to actually "use" Gen 1 Image Intensifying up to and including Gen 3, and with a range of Thermal Imaging, including military products.
OK, now before we continue, I believe it is important for the reader to be well aware that there is a LOT of "EXPERT" information provided on forums and industry web sites, regarding "seeing and detection distances etc." with night vision and thermal imaging.
A number of the claims and advice provided, can only be described as figments of wild imagination probably brought about by the use of "funny weed" and are simply not achievable.
There are at times the reverse, where it is said that it is all useless and no help in identifying a target reliably. You just need to understand what the benefits and limitations are.
A very common piece of advice given by "experts" on various forums both here and over seas, is that some cheap Chinese products, generally a basic digital product, will provide "stunning" performance ! (More on digital later)
If investigated further it will be found that the "expert" has never seen / used anything other the item being "recommended" and is unable to make a proper comparison, has therefore been impressed.
While it may seem to be great, because you can actually see more than with nothing, it suggests to a new user that they should rush out and purchase this "you beaut product", wasting money that can never be recouped.
One Australian business, claiming to be a major supplier of thermal equipment, the owner / technical adviser does not even know or understand which way IR frequencies and wave lengths vary with respect to temperature increases.
Don't be fooled by some well known brands, they are not necessarily all high specification items as they would like you believe.
Advertising is an art form.
Hopefully after going down these pages it will all become a little better understood.
First of all we need to understand that "Night Vision" was intended to enable us to see in the dark, not to be a long range observation device as are telescopes, binoculars etc.
Certainly as the technology advances we are able to see greater distances than in the past, and we are able benefit from it all.
OK, now let us look at what various types of "night vision" will give us.
Thermal imaging detects the "heat" in all objects, living or not, you need no light at all.
Thermal Imaging is true "IR", as it detects NOTHING but IR.
Image intensifying, the products that so many people call IR, requires light. Yes it will detect various wave lengths of IR, and also visible light, that is "multiplied" by the tube fitted in the device, it is NOT an IR device.
Digital devices (Other than GENUINE military devices) all require large amounts of light to perform with any degree of success.
This can be ambient visible light or additional IR. (see below comments regarding IR light)
They do NOT magnify the light like image intensifying equipment.
With thermal, obviously the greater the temperature difference, the greater one object will stand out from other surrounding objects.
For example, on a hot day in the "field", a small animal will not be easy to see against the surrounding hot ground, rocks etc. whereas at night in the same location it will stand out clearly.
But let’s think about that for a moment, why would you need thermal or any other night vision system in the daylight anyway?
A "live target" among rocks etc. that is a similar size to the rocks, that are still hot from the days sun, can be a little hard to distinguish until the rocks have cooled somewhat, therefore providing a greater temperature difference between them and the target. Naturally enough a moving target will be obvious. (Rocks do not normally move ! ....Hopefully)
Something that should be pointed out here regarding thermal, is that "detection" distances quoted by various manufacturers should be viewed cautiously, as they are based on calculated distances and NOT actual distances.
Therefore some figures may be considered to be a little "generous", where one manufacturer with a particular specification will state one distance while another manufacturer using exactly the SAME SPECIFICATION will indicate a different distance.
As the user has no way of actually confirming the figures a little thought may be needed.
So in fact the one stating say, 1660 m, will be no different in performance to another indicating 1800 m, when they have the SAME SPECIFICATIONS.
These figures are commonly quoted being around the mid distance between the calculated minimum and maximum ranges.
This is not a fault of the manufacturers as they can never predict what conditions a user will encounter. Therefore all they can do is provide a figure as an indicator only to give a basic starting point to compare models with each other.
Sensitivity is included the "Facts about Thermal" page.
Image intensifying requires some LIGHT, whether it is the ambient light generated by stars, moon or an external infrared light source, and amplify whatever light is available.
Although the night is never TOTALLY dark, it will require no less than Gen 3, and at the same time will need at least starlight available, to produce basic a workable image, or an external IR light source, which can in turn, create a problem with nocturnal animals (see below).
Digital however, only detects what the ambient or external light / IR, that is intense enough to produce an image. This is limited by the sensitivity of the sensor fitted and does NOT "magnify" any available light.
Digital equipment, other than that produced specifically for military use, (with an appropriate price tag) should really be viewed as a consumer product at this time due to its inherent requirement of VERY HIGH levels of light, IR or natural visible, to provide any worthwhile detection range at night, even though digital may produce a very good resolution image.
Therefore it can hardly be considered real "night vision" regardless of what resolution quality it may or may not have.
Remember, the actual IR light can be seen by nocturnal animals as well as the visible red light generated by the illuminator that is VERY VISIBLE, and a high power illuminator will show an INTENSE red light which can be seen EXTREMELY well from the "targets" direction.
"Covert" IR with it's longer wave length is less noticeable when viewed directly at the source, it has been hinted in some scientific papers even the covert IR (920-940 nm wave length) light produced, can still be seen by nocturnal animals.
Covert IR is not detectable by all devices and will not provide the same "range" as shorter wave lengths.
This applies to any "NV" system requiring additional IR !
Unfortunately there are MANY people who claim that it is not so, and IR will NOT disturb animals.
We can probably all relate to the use of spotlights in the past, for a time the animals reacted, but generally not greatly, until they became educated to the situation and then VERY wary and virtually unapproachable.
It WILL happen with Infrared light, whether you wish to admit it or not.
Any way, why on earth would I spend my money on a "NIGHT VISION" device and then be required to provide a light to make it work ????? (For a while)
There is a general consensus is that Image Intensifying units will provide more detail or definition of the "target" when compared with thermal imaging, this is "technically" correct, but regardless, you will still NOT see a "desired target" in dark shadows etc., whereas thermal will make these stand out and be visible without question. (See the image on the "facts about thermal" page)
For example, a high end Gen 3 unit can provide an exceptional image in the right conditions, but even so, you will still need a high contrast "target" to stand out from the background and surrounding objects.
The higher specification models of thermal imaging now provide the user with outstanding detail giving the best of both worlds.
There are also units combining thermal and digital, but unfortunately they are usually out of reach of the general "public", as are some of the new High Spec thermal only products.
Do not expect to get the same performance from a $500 NV item that you will get from one costing $30,000!
This in no way implies that ONLY professional grade equipment should be considered.
Commercial products are a proposition in some situations, but $500 will not buy anything but toys.
If you intend to make observations, for example, from inside a motor vehicle or inside a building, thermal imaging will not "see" through glass windows, while image intensifying can be used but with a reduction in performance (DRI).
When making a choice of a system type to use, remember that any type of night vision that requires some degree of light (image intensifying and digital), will have difficulty when trying to observe something or someone when they are partially covered or concealed behind bushes, trees, in shadows etc.
Thermal will "see" any part of the target that is not completely covered, even in total darkness.
The use of infrared illumination will only provide limited benefit when used in attempting to light up between the bushes. All that will be seen is the IR glare reflected of the face of the bush, just as that observed when using a spotlight in the same situation.
Having said that, a "hot" target completely covered by an object which prevents any heat being radiated, will not be seen with thermal imaging either.
Various "generations" of image intensifying night vision exist, Generations are military designations and these start at Gen 1, there is mention of Gen 0, a non military term, at times, and go up to Gen 3, plus various "improvements" after that. Generation 4 * (see below) is also referred to at times but it is not an official classification.
For example, * PHOTONIS 4G, see below.
The Generations relate to changes in technology, and in turn their performance in low light conditions, and at the same time image quality improves accordingly.
The greater number of line pairs per mm (lp / mm) the better the image resolution produced but will not substantially increase the detection distance, UNLESS you have increased LIGHT MAGNIFICATION as well.
There are other improvements as generations go up, such as signal to noise ratio which is an important part of seeing an object clearly, especially in adverse conditions.
Prices naturally increase relative to their performance. It is important to be aware of just what the differences actually are. Unfortunately it is difficult to explain all this in text. It is always beneficial to discuss this in detail with us prior to making a decision what may be applicable for the job at hand.
One difference between types of night vision systems that may influence selection for a shooter, is that with the use of IR illumination with image intensifying units, "eye shine" can be detected. Thermal imaging will not produce this effect, as no illumination is required, therefore there is nothing to be reflected back to the shooter.
A situation to consider, for instance, even a medium sized animal in a “clear” paddock with average pasture, at 100 – 200 +M, thermal imaging will clearly indicate a warm “target” is there, even partially obscured by grass or in shadows, you may not see enough of it to properly identify what it is, but you will know it is there.
Changing from thermal for spotting to an image intensifying NV scope to shoot, a common suggestion, even with Gen 3, the "target" will tend to blend into the shadows and shapes in the grass and can be very difficult to even see, (unless it is a high contrast target), even though it is widely claimed that this type of equipment will (supposedly) provide better definition of the target than thermal.
* PHOTONIS have now released a "4G" tube (not "Gen 4" but Gen 2) which has some modified specifications over their XR5 (Gen 2) tubes. Basically the XR5 has better signal to noise ratio and an improvement to average lp / mm over "normal" Gen 2.
There is also some improvement to the EBI etc.
Unfortunately the light amplification is still low (Gen 2 level). Gen 3 has a 30% greater light gain, therefore producing a brighter image overall for any given light conditions.
The 4G tube has the ability to use a longer wave IR (1000 nm). This will not provide any benefit to most users regardless of the extra money required.
Site updated, SEPTEMBER 22, 2021.