When you start comparing modern thermal cameras, you quickly notice one figure that manufacturers almost always emphasise.
NETD.
Some models state below 40 mK.
Others below 25 mK.
The newest and most expensive devices even below 20 mK.
But what does that actually mean?
Does the hunter notice the difference in the forest, or is it just marketing?
The answer is simple.
Yes, they do.
But not always where most buyers expect.
What is NETD?
NETD (Noise Equivalent Temperature Difference) shows how small temperature differences the thermal camera's sensor can distinguish.
Put simply:
the lower the NETD number, the more sensitive the sensor.
And the more sensitive the sensor, the more detail you see.
For example:
A 40 mK sensor sees strong temperature contrasts well.
A 25 mK sensor sees more small details.
A 20 mK sensor sees even finer differences.
On paper the difference seems small.
In practice it can change the whole observation experience.
When does NETD not play a big role?
Let us imagine a cold January evening.
The air temperature is –10 °C.
A wild boar is crossing a snowy field.
In such a situation the animal stands out very well with almost any quality thermal camera.
The temperature difference between the animal and the background is large.
The contrast is strong.
In such ideal conditions the average hunter may not notice much difference between a 40 mK and a 20 mK sensor.
Many buyers make a mistake here.
They try the devices in ideal conditions and conclude that they all perform the same.
Estonian weather is not ideal
In reality, most hunting takes place in much more difficult conditions.
Autumn.
Rain.
Fog.
Damp forest.
Thaw.
Wet ground.
This is where NETD really gets to work.
The smaller the temperature difference between the animal and its surroundings, the harder it is for the animal to stand out from the background.
In such situations a better sensor shows more detail.
And this difference is often very clearly visible.
40 mK vs 25 mK – what does the hunter see?
At 300 metres both devices may show the animal.
But the difference is in the details.
40 mK sensor:
- the animal is visible
- the silhouette is there
less detail.
25 mK sensor:
- body outlines are clearer
- the legs stand out better
- the shape of the head is more visible
movement is easier to assess.
This means the animal is not just a warm dot.
It becomes a more recognisable object.
25 mK vs 20 mK – is there a difference?
Yes.
But it is smaller than the difference between 40 mK and 25 mK.
A 20 mK sensor becomes especially valuable:
- in rain
- in fog
- in damp forest
- early in the morning
- on an autumn field
in difficult temperature conditions.
These are situations where even small details can help make the right decision.
Does NETD affect the detection range?
Not directly.
A mistake is often made here.
The detection range is mainly affected by:
- lens size
- sensor resolution
optical quality.
NETD primarily affects how much detail you see.
You may spot the animal with both devices.
But a device with lower NETD helps you better understand what you are actually looking at.
Why do professional hunters talk about NETD so much?
Because experience teaches.
Over the years it becomes clear that most hunts do not take place in ideal conditions.
True quality shows when:
- it is raining
- fog drifts across the field
- the forest is wet
the air temperature is close to zero.
That is when the better sensor starts to give an advantage.
This does not necessarily mean more visible animals.
It means more visible detail.
And detail helps you make better decisions.
Higher resolution or better NETD?
This is one of the most popular questions.
If you compare:
- 640×480 sensor + 40 mK
- and
- 384×288 sensor + below 20 mK
then the answer is not always simple.
Both features are important.
Ideally the hunter should get:
- high resolution
- a low NETD value
quality optics.
These three features work together.
Deciding on the basis of just one figure can be misleading.
Which NETD values are good in 2026?
Below 40 mK
A good average level.
Suits many hunters.
Below 25 mK
A very good level.
Offers noticeably more detail in difficult conditions.
Below 20 mK
Top level.
Maximum sensitivity and richness of detail.
Suits the demanding user.
Is a thermal camera with higher NETD bad?
Certainly not.
Many successful hunters use devices with NETD below 40 mK.
It is important to understand that hunting success does not depend on a single number.
Experience, observation skills and correct use always remain the most important.
NETD simply helps you see more.
Summary
If you hunt mainly in ideal conditions, the difference may not seem very big.
But if you spend a lot of time in the forest, on fields and in changeable weather, low NETD quickly becomes one of the most important features.
40 mK helps you spot the animal.
25 mK helps you assess the animal better.
20 mK helps you see detail even when the weather is working against you.
That is why NETD should not be seen as just a technical number.
It is one of the main reasons why two similar-looking thermal cameras can give completely different results in the forest.
A good thermal camera does not just show heat.
A good thermal camera shows the details that help the hunter make the right decision at the right moment.