Thermal Imaging Camera Resolution: How Many Pixels Do You Need

Resolution vs Image Quality

Thermal imager specifications often advertise pixel counts like 160x120, 320x240, or 640x480. Higher numbers do not automatically mean better measurements - what matters is how those pixels map onto your target at the working distance.

IFOV and MFOV Explained

IFOV (instantaneous field of view) is the angle subtended by a single detector pixel. MFOV (measurement field of view) is the angle needed to obtain an accurate temperature reading - typically 3 times the IFOV. Both are expressed in milliradians (mrad).

Spot Size Calculation

Spot size = distance x IFOV. For example, a camera with IFOV of 1.36 mrad measuring at 5 meters has a spot size of 6.8 mm. To accurately measure a target 10 mm wide, the MFOV must fit - so distance must be no more than half the spec sheet maximum.

Choosing Resolution by Application

• Building envelopes: 160x120 sufficient for most home inspections.
• Electrical panel surveys: 320x240 minimum to resolve individual lugs at 2-3 m.
• PCB and component analysis: 640x480 with macro lens.
• Substation and tall tower inspections: 640x480 with telephoto lens.

Other Decisive Specifications

• NETD: thermal sensitivity, lower is better (0.05 K is professional grade).
• Frame rate: 30 Hz or higher for moving targets.
• Temperature range: -20 to 650 C covers most industrial scenarios.
• Optional lenses: macro, telephoto, and wide-angle add flexibility.

EK Recommendation

For industrial electrical inspection, a 384x288 or 640x480 detector with NETD <0.05 K and interchangeable lens system delivers the best balance of resolution, range, and budget.