How do I take a good infrared thermal image?

Using modern handheld thermal imaging cameras is quite simple, BUT interpreting the images captured takes knowledge, training and experience.  To help you prepare and capture the best thermal image to analyze, there are four camera adjustments that you should address.

  • The first is camera focus.  Some infrared camera come with a fixed focus lens.  Focusing these imagers requires skill to find the best “sweet spot” distance from your target which provides the clarity of detail in the image that you require.  For infrared cameras with manual focusing capability, the onus is on you to take your time tightly focusing your target to lock in the clearest focused image when you capture the picture.  The more sophisticated infrared cameras have either an auto-focus or a push button auto-focus feature.  Both of these options provide good focusing of the camera but also require diligence on your part as they are not as consistent as your hand-eye coordination of a manual focus.  Focus is one of the keys to successful thermographers.  You cannot change the focus of a captured IR image with PC software later.  So take your time and get it right the first time!
  • The second is changing the emissivity setting of the camera.  Emissivity is the amount of radiation emitted from an object compared to that of a perfect emitter of radiation when both are at the same temperature.  A lower emissivity setting would be used for highly reflected objects and a high emissivity setting would be used for low reflective objects.  Objects that are non-metal or that have a rougher surface will have a higher emissivity.  Adjusting the emissivity is important when taking temperature measurements or when comparing two different objects’ temperatures.  Incorrect emissivity settings will make objects appear hotter or colder then what they really are.  Not all infrared cameras will allow the user to adjust the emissivity of the imager.  Lower cost IR cameras may be locked into a default emissivity for wood or drywall.
  • The third is adjusting the camera for reflected temperature.  The reflective temperature setting allows you to compensate for temperatures from surrounding objects reflecting on your target object.  If reflected thermal energy from surrounding objects is suspected, move the camera around in the area of the target and see if the hot or cold spot moves with the camera.  If it does, it is a reflection from another object, if it does not, it is a true hot or cold spot.  In order to find out what the reflective temperature is, you will need to adjust the emissivity of the camera to 1.0, then place a piece of crinkled aluminum foil on a piece of cardboard.  Hold the foil between the camera and the object you intend to view and note the temperature of the foil. Then input the temperature of the foil into the reflective temperature setting for your infrared camera.  Just like emissivity, reflective temperature is important when taking temperature measurements or comparing temperatures of two or more objects.  Again, not all infrared cameras will allow you to input the reflective temperature.
  • The fourth is thermal tuning.  Thermal Tuning of your infrared camera involves adjusting the span or temperature range that the camera sees while in manual viewing mode.  Infrared cameras today usually have an automatic viewing mode and a manual viewing mode.  When the imager is in automatic mode, the camera will automatically adjust the temperature scale to what is being viewed (your target area) which causes the display to change colors frequently when the camera is moved from place to place.  Manual mode allows you to adjust the span to a desired range.  Then the camera will always display this temperature range or span until you switch back to automatic mode.  Using the manual mode is best used to bring out temperature differences of the object being viewed.

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For over 33 years Monroe Technology has been there for the professional thermographer. Monroe Infrared helps clients understand, select and train to maximize the value achieved with the right infrared camera.  Contact us to discuss and review your applications, expectations and budget constraints. 

The i-Series is a great tool for those who are in the trenches. Put the i-Series in your tool box today and use the power of infrared to visually detect problems before they detect you. Please contact us to discuss and review all of these as necessary to ensure you make the best decision for your business!

Infrared Technology Knowledgebase