Thermal sensor resolution is the pixel grid behind the glass: 384×288, 640×480 or 1280×1024. It does not by itself set how far a scope or monocular can detect a warm body (that is mostly down to lens size and sensitivity), but it does set how many pixels fall on that body once you have found it, which decides how far you can zoom digitally before the picture turns to coloured mush. Here is the maths behind that, worked through with two real units at opposite ends of the resolution scale.
| What you need | What to look at |
|---|---|
| Scanning paddocks or a creek line for pests within about 1,200m, carried all night | Native resolution and weight: HIKMICRO Lynx LH25 3.0 Thermal Monocular |
| Long shots out past 1,000m where you need to confirm species before you commit | Pixel count plus a built-in rangefinder: Guide TU1250M 3.0 Thermal Scope |
| One optic for daylight glassing and night thermal, no swapping scopes | Dual-spectrum thermal and digital channel: Guide TU1250M 3.0 Thermal Scope |
What 384, 640 and 1280 actually mean
These numbers describe the pixel grid of the thermal detector itself, the same idea as megapixels on a camera, just much smaller because a thermal sensor is expensive to build at high pixel counts. A 384×288 sensor has 110,592 pixels. A 640×480 sensor has 307,200, nearly three times as many. A 1280×1024 sensor has 1,310,720, almost twelve times the pixel count of the 384 class. More pixels means more of the scene is resolved into individual temperature readings rather than blended together into one blob.
But pixel count on its own does not tell you how much detail lands on your target. That depends on two more things: the physical size of each pixel (pixel pitch) and the focal length of the lens in front of it. Together they set the angle of scene each pixel covers, which is what actually determines how many pixels end up across a fox, a pig or a person at a given range.
Pixels on target: the maths that actually matters
Angular resolution per pixel (often called IFOV) is pixel pitch divided by focal length. Both the units featured here use a 12μm pixel pitch, so the difference in detail per pixel comes down to the lens. Guide TU1250M 3.0 pairs its 1280×1024 sensor with a 50mm F1.0 lens: the thermal resolution is 1280×1024 @ 12μm with NETD 18mK, paired with a 50mm F1.0 objective lens, which works out to roughly 24mm of scene per pixel at 100m. The HIKMICRO Lynx LH25 3.0 uses a 384×288 sensor with a 25mm lens, and its confirmed spec sheet lists a Pixel Interval: 12 μm with a Field of View (H × V): 10.5° × 6.4° / 18.4 m × 11.2 m @ 100 m, which works out to roughly 48mm of scene per pixel at the same 100m, almost exactly double.
Worked example: pixels across a feral pig at 100, 300 and 500m
Take a feral pig's chest or shoulder, broadside, at roughly 400mm wide. Multiply each sensor's per-pixel figure by the range and divide it into 400mm to see how many pixels land on the animal.
| Range | Guide TU1250M 3.0 (24mm/pixel at 100m) | HIKMICRO Lynx LH25 3.0 (48mm/pixel at 100m) |
|---|---|---|
| 100m | about 16 pixels across | about 8 pixels across |
| 300m | about 5 pixels across | about 2 pixels across |
| 500m | about 3 pixels across | about 1 pixel across |
This assumes a 400mm-wide target held broadside, horizontal pixel pitch only, clear air and pixel counts rounded down. Real-world clarity also depends on haze, the temperature contrast between animal and background, and how still the target is holding.
Detection, recognition and identification are different jobs
As a rough rule of thumb used across the thermal industry, a target needs only a pixel or two to register as a hot spot (detection), several pixels before you can tell its general shape and size (recognition), and a dozen or more before you can be confident of species or that it is safe to shoot (identification). Run that against the table above: at 500m the LH25 3.0 is giving you one pixel, enough to know something warm is out there but not enough to identify it unassisted. The TU1250M's three pixels at the same range is still thin, but it is backed by a longer native detection range and more headroom to zoom in before you reach that limit.
Why detection range and resolution are not the same thing
It is tempting to assume the sensor with more pixels always sees further, but detection range is driven mainly by lens aperture and sensor sensitivity (NETD), not pixel count. The TU1250M's thermal detection range extends to 2600m (2800yd), more than double the LH25 3.0's confirmed 1,200m. Part of that gap comes from the bigger 50mm F1.0 objective gathering more of the scene per pixel over distance, not purely from having more pixels. NETD matters too: lower is more sensitive to small temperature differences, and the LH25 3.0's detector is rated at NETD under 15mK against the TU1250M's 18mK, so a smaller sensor can still be very good at picking up faint heat signatures, it just has fewer pixels to spread across the target once found.
Digital zoom quality: why pixels run out
Every thermal device lets you zoom past its base magnification, but digital zoom does not add detail, it enlarges the pixels you already have. Once you are past the sensor's native resolution, you are looking at bigger blocks of the same information, not new information. This is true even with processing tricks: HIKMICRO's AI-based Image Pro 3.0 and Zoom Pro algorithms intelligently enhance detail and clarity across the zoom range on the Lynx LH25 3.0, which sharpens edges and contrast as you zoom, but it is working with the same 384×288 pixel grid underneath. The same logic applies to the TU1250M's screen: its 1.03-inch AMOLED display runs at 2560×2560 resolution, well above the thermal sensor's native 1280×1024, because the display is scaling up for a sharp sight picture, not inventing extra thermal detail. A sensor with more native pixels simply gives any zoom or processing more real information to work with before it runs out.
Is the step up from 384 worth it?
When a 384 class sensor is enough
If most of your work happens inside a few hundred metres, scanning a paddock boundary, checking a dam bank or spotting movement in timber before you close the distance, a 384×288 sensor paired with a fast lens does the job well and keeps the unit light. The LH25 3.0 weighs just over 320g, which matters when you are carrying it for hours rather than mounting it on a rifle. For more on where a handheld thermal earns its keep, see our piece on the advantages of night vision thermal monoculars and our guide to thermal vision for hunting.
When the jump to 1280 pays off
If you are regularly shooting or confirming targets past 300 to 500m, the extra pixel count stops being a nice-to-have and starts being the difference between a confident identification and a guess. Pair that with a built-in laser rangefinder, which on the TU1250M reaches out to 1,500m, and you are ranging and confirming the same animal rather than estimating holdover on a hunch. If you are weighing up a dedicated scope against a handheld unit for hunting, our guide on selecting the right hunting scope and our explainer on thermal vs night vision are worth a read before you commit.
There is a middle ground too. A 640×480 sensor sits between the two units featured here: roughly three times the pixel count of a 384 class detector but still well short of a 1280 flagship, and it is a common choice for shooters who want more pixels on target than an entry monocular offers without paying for the top tier. If you are comparing a 640 class option against what is in the thermal collection, run the same pixel-pitch and focal-length maths above against its spec sheet before you buy.
Frequently asked questions
Does a higher resolution sensor mean a longer detection range?
Not directly. Detection range is driven mostly by lens aperture and sensor sensitivity (NETD), which is why the TU1250M's 2,600m range comes largely from its 50mm F1.0 lens rather than its pixel count alone. Resolution decides how much detail you get once something has been detected, not how far you can first spot it.
What does NETD mean and does it matter as much as resolution?
NETD is the smallest temperature difference the sensor can resolve, so a lower number means it is more sensitive to faint heat signatures. It matters alongside resolution rather than instead of it: a sensitive sensor with few pixels can still find an animal in poor conditions, it just has less detail to work with once it does.
Can digital zoom make up for a lower resolution sensor?
Only to a point. Digital zoom enlarges the pixels you already have rather than adding new ones, so a 384 class sensor zoomed in hard will always show blockier detail than a 1280 class sensor at the same zoom level, even with AI sharpening applied.
What resolution do I actually need for fox or pig work on an Australian property?
If most shots and sightings happen within a few hundred metres, a 384×288 sensor like the one in the Lynx LH25 3.0 is usable for spotting and confirming. Once you are regularly working past 300 to 500m or need a built-in rangefinder to commit to a shot, the extra pixels and reach of a 1280 class unit like the TU1250M start to earn their keep. Always check your state's firearm and permit rules before heading out, as they vary across Australia.
Still not sure which one suits you?
Tell us what you are hunting, the typical ranges you work at and whether you need it mounted on a rifle or carried in hand, and we can point you to the right sensor size. Get in touch or browse the full thermal collection to compare specs side by side.
