Thermal Camera Specifications, From Pixel Pitch to DRI Range
A reference for reading an infrared camera data sheet the way a specification actually behaves in the field. Each parameter is explained by what it controls, how it interacts with the others, and what to ask a supplier before you commit.
The Parameters, and What Each One Really Controls
| Specification | What it controls | What to ask the supplier |
|---|---|---|
| Detector format 256×192 / 384×288 / 640×512 / 1280×1024 |
The ceiling on detail and range. It also fixes the aspect ratio and the horizontal field of view you get from a given focal length. | Is the stated format the native array, or an interpolated output resolution? |
| Pixel pitch 17μm legacy, 12μm current uncooled VOx |
How much resolution fits in a given detector area. Smaller pitch means more pixels without a larger lens. | What is the native pitch, and does the lens image circle cover the full array? |
| Focal length | Magnification and range. Inversely related to field of view for a fixed detector. | Which focal lengths are available for my detector format, and at what f-number? |
| Field of view (FOV) | How much scene you cover. Derived from detector width, pixel pitch and focal length. | Is the quoted FOV horizontal, vertical or diagonal, and is it measured or calculated? |
| IFOV pixel pitch ÷ focal length |
The smallest resolvable angular detail; the basis for all DRI arithmetic. | Can you state IFOV in mrad for the exact lens I am buying? |
| NETD millikelvin sensitivity |
How small a temperature difference is visible above sensor noise. Lower is better. | At what f-number and frame rate was it measured? |
| Frame rate 25/30 Hz, 50/60 Hz, 100+ Hz |
Motion capture and PTZ smoothness; drives bandwidth and storage proportionally. | Is the full frame rate available at full resolution, and at what bit depth? |
| DRI ranges EN IEC 62676-4 |
The defensible statement of what the camera can do at distance for procurement. | Which pixel criterion and critical dimension were assumed? |
Reading the Four Relationships That Cause Most Specification Errors
1. Resolution and field of view are coupled through the lens
The same 25mm lens produces a wider field of view on a 1280×1024 sensor than on a 640×512 one, because a wider array subtends more of the image circle. This is why HD is not only a range upgrade: it is also a coverage upgrade at equal DRI performance.
Practical consequence: when you move detector format, recompute field of view. Do not assume the coverage you had before.
2. Sensitivity trades against range
A high-resolution detector with poor NETD produces noisy, low-contrast imagery at long range, where signal is weakest. A lower-resolution detector with better NETD often delivers more actionable images in fog, maritime or low-contrast scenes.
Practical consequence: evaluate resolution and NETD together. Neither alone predicts field performance.
3. Frame rate scales cost downstream, not just in the sensor
Doubling frame rate roughly doubles raw data rate, which propagates into encoder capacity, network bandwidth, storage sizing and analytics compute. The sensor may support it while the rest of the system cannot.
Practical consequence: size bandwidth and storage from the highest frame rate you will actually run, not the default.
4. DRI is a derived number, not a sensor property
Detection, recognition and identification ranges follow from focal length, pixel pitch and the pixel criteria in EN IEC 62676-4. The same core yields very different DRI figures with different optics, so a quoted range without the lens is not a specification.
Practical consequence: always quote DRI together with the exact focal length, and verify it with the DRI calculator.
What This Guide Does Not Cover
This page is deliberately about the optical and sensor specification layer. For the full six-step selection process that starts from the application and ends with compliance, use the thermal camera buying guide; for detector technology, cooling and LWIR versus MWIR physics, see the technology guide; for module-level trade-offs between resolution, NETD and frame rate, see the thermal module selection guide.
Need a Specification Review Before You Quote?
Send us the requirement — range, target, environment and interface — and we will tell you which specification actually governs it.