Detector resolution, focus and distance: what really changes the detail?

Start with the native detector

The native detector resolution describes the grid of sensing elements. An enlarged output, sharpened image or enhanced display can be easier to look at without containing the same amount of newly measured spatial information.

Gough's P3 review compares native capture with enhancement modes and discusses processing artefacts. When judging detail, ask what the sensor measured and what software added to the presentation.

Count coverage, not just pixels on the box

The same detector can cover a wide room or a small board depending on its lens and distance. As the camera moves farther away, a small target generally occupies less of the detector. If the target is not sufficiently resolved, nearby cooler surfaces can reduce the apparent peak.

IRINFO's spatial-resolution article illustrates this with different cameras viewing equipment targets. It is a historical, manufacturer-affiliated field comparison with stated limitations, not a ranking of current products.

A thermometer has a measurement area too

Distance-to-spot information describes the relationship between distance and a thermometer's measurement area. As a simple illustration, a nominal 12:1 ratio at 1.2 metres suggests a spot around 0.1 metres across. Real instruments may have an offset, a minimum distance and a stated energy-coverage definition; use the model's manual.

The target should comfortably cover the relevant measurement area. The laser point does not show that area and does not make a tiny target measurable.

Compare cameras at the distance you will use

For a buying comparison, use the same target and similar operating conditions. Record field of view, working distance, focus, native resolution and processing mode. Show both the full scene and a clearly labelled crop.

Ask two separate questions: can the image identify the feature, and can the instrument measure its temperature adequately? A visually recognisable part is not automatically a valid quantitative target.

• Read the native resolution separately from exported image dimensions.
• Check focus and field of view at the intended distance.
• Look for a small-target demonstration, not just a room overview.
• Treat enhancement as a processing mode, not a new detector.