384 vs 640 Thermal Sensors: What the Numbers Really Mean

384 or 640? It's the question that decides most thermal scope purchases — and the marketing answer ("640 is better") is misleading. The truth is more useful: at the same lens, a 384 and a 640 reach about the same distance. What changes is the field of view. This guide explains what the numbers really mean so you can buy for the way you hunt, not the bigger sticker.

Quick answer

For a given focal length and pixel pitch, a 384 and a 640 sensor give you roughly the same detection and identification distance. The 640 shows a wider field of view — more of the paddock in frame, better for scanning and keeping moving game in view up close. The 384 shows a narrower, more magnified slice — and costs less. So it's not "640 sees further"; it's "640 sees wider, 384 sees tighter for the money."

What the numbers actually describe

384×288 and 640×512 are pixel counts — how many detector elements the sensor has. Paired with that is pixel pitch (measured in microns, µm), the size of each pixel. Pitch is what sets the angular detail per pixel; the pixel count sets how much scene the sensor covers. Two sensors with the same pitch on the same lens resolve the same fine detail per pixel — the 640 just covers more area because it has more pixels.

That's the heart of it: more pixels = more scene, not more reach. Detection distance is driven by the lens and pitch, which both sensors here can share.

Same lens, same range — wider view

Put a 384 and a 640 of the same pixel pitch behind the same lens and you get the same pixels-on-target at distance, so detection and identification land at similar ranges. The difference you'll see immediately is the field of view. As a worked example, with 12µm pixels on a 50mm lens a 640 shows roughly an 8.8°×7° field of view, while a 384 shows about 5.3°×4° — noticeably narrower and therefore more magnified at base.

Neither is "better" in the abstract:

So which should you choose?

• Choose a 640 if you scan a lot, hunt mobile game like pigs in mobs, or want the most situational awareness and the easiest picture to read. The wide field of view keeps moving animals in frame and makes identification more confident at distance.
• Choose a 384 if you want the most capability for your money and you mostly take deliberate shots at range, where the naturally narrower, more magnified view is an advantage. It detects game just as far on the same lens.

And don't forget pixel pitch: a smaller pitch (12µm) packs detail tighter for sharper distant edges but a narrower view, while a larger pitch (17µm) collects more energy per pixel, which can help in low-contrast conditions. Compare lens, pixel count and pitch together — not the resolution number alone.

FAQ

Is a 640 thermal scope better than a 384?

Not universally. At the same lens and pixel pitch they detect and identify at similar distances. The 640 gives a wider field of view and easier scanning; the 384 gives a more magnified view for less money. The "better" one depends on how you hunt.

Does a 640 sensor see further than a 384?

No — not on its own. Reach is set by the objective lens and pixel pitch. A 640 mainly widens the field of view. See our guide on detection range and lens size.

What does pixel pitch (12µm vs 17µm) change?

Pitch sets the detail per pixel and influences field of view and low-light sensitivity. Smaller pitch (12µm) = finer distant detail and a narrower view; larger pitch (17µm) = more energy per pixel, which can help in poor contrast. It's as important as the resolution count.

If they reach the same distance, why buy a 640?

For the wider field of view and easier identification across a broader scene — genuinely valuable for scanning and moving game. Just don't buy it expecting extra range; buy it for the view.

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