5.4: Key Camera Performance Specifications

Understanding camera specifications helps Level I technicians select appropriate equipment for a given inspection, when directed by procedures.

Thermal Sensitivity (NETD)

Noise Equivalent Temperature Difference (NETD) describes the camera’s ability to detect small temperature differences.

• Lower NETD values indicate better sensitivity
• Important for detecting subtle thermal contras

Table 5-1: Thermal Sensitivity (NETD) Comparison

NETD Value (mK)	Sensitivity Description	Typical Applications	Level I Relevance
< 30 mK	Very high sensitivity	Research, precision inspections	Awareness only
30–50 mK	High sensitivity	Electrical, mechanical, building inspections	Ideal for Level I
50–80 mK	Moderate sensitivity	General condition monitoring	Acceptable for training
> 80 mK	Low sensitivity	Limited applications	May miss subtle anomalies

Note: Lower NETD values allow detection of smaller temperature differences.

Table 5-3: Infrared Camera Spectral Range

Spectral Range	Wavelength (µm)	Common Applications	Notes
SWIR	1–3	High-temperature, specialty	Rare in Level I
MWIR	3–5	Gas detection, high-temp targets	Typically cooled systems
LWIR	8–14	Electrical, mechanical, building, drone	Most Level I cameras

Spatial Resolution

Spatial resolution refers to the number of pixels in the detector array, such as:

• 160 × 120
• 320 × 240
• 640 × 480

Higher resolution allows better detail and smaller target detection, especially at greater distances.

Table 5-2: Infrared Camera Detector Resolution Comparison

Detector Resolution	Typical Use Cases	Advantages	Limitations	Level I Notes
160 × 120	Basic inspections, training, short-range work	Lower cost, simple operation	Limited detail, small targets difficult to resolve	Suitable for introductory labs
320 × 240	General industrial inspections	Balanced resolution and cost	Reduced effectiveness at long distances	Common Level I field camera
640 × 480	Electrical, mechanical, building, aerial inspections	High detail, better small-target detection	Higher cost, larger data files	Preferred for drone thermography

Instantaneous Field of View (IFOV)

IFOV describes the angular size of a single pixel. Smaller IFOV values mean each pixel represents a smaller area of the target.

IFOV is critical when inspecting small components or when working at long distances, including aerial inspections.

Table 5-4: IFOV and Distance Impact on Measurement

Distance to Target	IFOV Impact	Measurement Risk	Level I Guidance
Close range	Small pixel area	Low	Preferred when possible
Medium range	Moderate pixel area	Moderate	Verify target fills pixels
Long range	Large pixel area	High	Risk of averaging errors

Key Principle: The target must fill multiple pixels for reliable measurement.

Distance-to-Spot Ratio

Distance-to-spot ratio describes how distance affects the minimum size of a measurable object.

As distance increases:

• The measurement area increases
• Small targets may be averaged with surrounding areas

Spectral Range

Most industrial cameras operate in the 8–14 micrometer (µm) long-wave infrared range. This range is well suited for typical inspection temperatures and environmental conditions.

Wide, Standard, Telephoto Lenses

In photography, there are different types of lenses that provide an array of different perspectives. In thermal imaging, lens choice (wide, standard, telephoto) dictates your Field of View (FOV) and magnification, crucial for matching the camera to the task: wide-angle (large FOV) captures big scenes or close objects; standard (medium FOV) is versatile for general use; and telephoto (narrow FOV) zooms in on small, distant targets like power lines, enabling safe, detailed inspection from afar. The right lens makes the subject fill the frame for best resolution, balancing distance and detail.

Lens Types & Applications

Wide-Angle Lens

Characteristics: Larger FOV (e.g., 45°+), shorter focal length.

Best For: Scanning large areas (roofs, walls), tight spaces, or getting detailed views of nearby objects (thermal windows).

Example Use: Home inspections, large industrial scans, finding heat leaks in buildings.

Standard Lens

Characteristics: Moderate FOV (around 25°), good balance.

Best For: General-purpose inspections where you don't need extreme wide or narrow views.

Example Use: General electrical inspections, most everyday tasks.

Telephoto Lens

Characteristics: Narrower FOV, longer focal length, higher magnification.

Best For: Viewing small targets from a significant distance safely.

Example Use: Inspecting overhead power lines, high-voltage equipment, or distant ductwork from the ground.

Table 5-6: Common Infrared Lens Options

Lens Type	Field of View	Typical Applications	Limitations
Wide-angle	Large area coverage	Building surveys, roofs	Reduced spatial detail
Standard	Balanced	General inspections	Limited long-range
Telephoto	Narrow	Distant targets	Sensitive to motion