How to Choose a Thermal Camera: A Guide to Resolution and Emissivity

Stepping into the world of thermal cameras can feel like learning a new language. The spec sheets are a jungle of acronyms and numbers: NETD, FPA, FOV, and more. But amidst the noise, two specifications stand out as the absolute pillars that determine a camera’s performance and, ultimately, its value to you: Thermal Resolution and Emissivity.

Marketing departments love to flash big numbers, but a bigger number doesn’t always mean a better tool for your job. Understanding what these two core concepts actually mean in the real world is the single most important step you can take before spending your money. This is not a guide to tell you what to buy; it’s a guide to teach you how to think, so you can cut through the hype and choose with confidence.

Spec #1: Resolution - What You Can Actually See

At its simplest, thermal resolution is the number of heat-detecting pixels on the camera’s sensor. It’s written as Width x Height, like 80x60 or 160x120. A device like the Hti-Xintai HT-18 has a 220x160 sensor, which means it contains 35,200 individual thermal pixels.

Think of it this way: A higher resolution thermal image is like a higher-resolution photograph. It contains more data points, resulting in a sharper, more detailed image. This isn’t just about pretty pictures; it has a critical, practical implication related to distance. Higher resolution gives you the power to accurately detect and measure smaller targets from farther away.

• An 80x60 (4,800 pixels) camera is great for close-up work. You can easily see if a whole component on a circuit board is hot or find a draft around a window frame you’re standing next to.
• A 220x160 (35,200 pixels) camera allows you to do that same job, but also lets you stand at the bottom of a telephone pole and clearly see which connector at the top is overheating. A home inspector can use it to scan a vaulted ceiling from across the room and spot a small area of missing insulation.

The Great Debate: Native Resolution vs. “Software Magic”
Here’s where it gets tricky. Some cameras use clever software to enhance a lower-resolution thermal image. A well-known example is FLIR’s MSX technology, which takes a standard visual image with a built-in regular camera and overlays the outlines (edges, text, numbers) onto the thermal image.

• The Advantage of MSX: It makes the thermal image dramatically easier to understand. You can read the label on a circuit breaker while also seeing that it’s hot. For many, this context is invaluable.
• The Advantage of Higher Native Resolution: As one user review comparing the HT-18 to a lower-resolution FLIR noted, the software can sometimes “blur” or obscure subtle thermal details. A higher native resolution sensor captures more genuine thermal data. It might not look as “sharp” in a photographic sense, but the thermal information itself is richer. If your task is to see the pure heat pattern of moisture spreading inside a wall, you might prefer the unadulterated, high-resolution thermal data.

The choice isn’t about which is “better,” but which is better for you. Do you need easily understandable context (MSX), or do you need to see the most detailed, raw thermal information possible (higher native resolution)?

Spec #2: Emissivity - The Secret Handshake for Accuracy

This is, without a doubt, the most important and most overlooked concept in thermography. Ignoring emissivity can make your expensive, high-resolution camera produce wildly inaccurate temperature readings.

Here’s the core idea: Different materials radiate heat at different efficiencies. Emissivity is a measure of this efficiency on a scale of 0 to 1. A perfect radiator (called a “black body”) has an emissivity of 1. * High Emissivity Surfaces (>0.9): Matte, non-metallic surfaces like wood, plastic, rubber, human skin, and black electrical tape are very efficient radiators. The heat they emit is a true representation of their surface temperature. * Low Emissivity Surfaces (<0.3): Shiny, unpainted metals like polished steel or aluminum are terrible radiators. They act like thermal mirrors.

If you point a thermal camera (with its default emissivity setting of ~0.95) at a shiny stainless-steel pipe, you are not measuring the pipe’s temperature. You are measuring a reflected temperature—likely your own body heat or the ceiling lights. The camera will give you a number, but that number will be meaningless.

How to Get an Honest Temperature Reading:
For diagnostic work where you’re just looking for hot spots (e.g., “that component is hotter than the one next to it”), you can often ignore emissivity. But if you need an actual temperature value, you have two options:
1. Adjust the Setting: If you know the material you’re measuring, you can adjust the emissivity setting in the camera’s menu.
2. The Pro Cheat: The easiest and most reliable method is to make the surface a high-emissivity surface. Place a small piece of black electrical tape (which has a known, high emissivity of ~0.95) on the shiny object. Wait a moment for it to equalize in temperature, then measure the temperature of the tape. This will give you a highly accurate reading of the object’s true surface temperature.

Your Decision Map: Matching Specs to Your Mission

• If you are a Homeowner/DIYer finding drafts and insulation gaps: A basic resolution (80x60 or higher) is often sufficient. Emissivity is less critical as you are looking for temperature differences.
• If you are an Electrician: Higher resolution is valuable for seeing small components from a safe distance. Understanding emissivity is absolutely critical for accurately measuring busbars and connectors.
• If you are a Home Inspector: Higher resolution is a major advantage for scanning large areas like roofs and ceilings efficiently. You’ll need both a good understanding of emissivity (for HVAC components) and potentially the contextual clues of an MSX-type feature.
  

Conclusion: Buy Knowledge First, Then the Tool

Don’t get hypnotized by the biggest numbers on the spec sheet. The “best” thermal camera is the one whose capabilities align with your needs and whose limitations you understand. By first investing a little time to grasp the real-world impact of resolution and the fundamental principle of emissivity, you transform yourself from a passive consumer into an informed buyer. You’ll not only purchase a better tool but, more importantly, you’ll know exactly how to use it to get reliable, meaningful results.