Practical tips and guidance for operating a thermal imaging camera.
Whether you’re just measuring the temperature of a small object or you’re evaluating differences in temperature across a wide area, when it comes to operating your thermal imaging camera there are always adjustments you’ll need to make before capturing any kind of image.
Firstly, once you’ve taken your camera from its case, you’ll need to let it take a few minutes to acclimatise to the air temperature around you. That’s because the temperature inside the camera needs to match the temperature outside it, otherwise you’re going to get inaccurate readings.
Then there are several options and settings that need to be decided upon, such as:
When operating a thermal camera, you can choose the most suitable image type for your purpose. It could be a regular visible light image – like that of an ordinary digital camera – or a false colour representation of temperature differences. Depending on your camera model you could also have the option of a picture within a picture … or an ordinary visible light image with an area converted to an infrared image.
A thermal camera “sees” temperature differences in terms of greyscale. But with over sixteen thousand different shades of grey between pure black and pure white – with differences too subtle for the human eye to detect – the camera needs to group shade values into easily-recognisable bands. Most thermographers, though, tend to convert those banded shades of grey into a colour scheme that goes from dark to light, to correspond to temperature differences. They can use different colour palettes which limit the range of colours in the final image, or which use the whole of the visible light colour spectrum for greater accuracy. (It’s always good practice to make sure whichever palette you select isn’t reversed, otherwise you’re going to get a totally different image which presents information that couldn’t be more wrong.)
As described in our emissivity article, all materials absorb, reflect and emit radiant energy, and emissivity is the measurement of how well an object’s surface emits heat in the form of infrared energy. The amount of that energy needs to be calculated, either through lookup tables or by comparing it with a surface with a known emissivity value. Then that amount needs to be input so the camera can deduct it from the total energy it’s detecting at the time to give an accurate reading.
The more moisture in the air between the camera lens and its target, the less accurate any reading is going to be, since moisture reduces the intensity of infrared energy emitted by the target. So it’s essential to gauge how much humidity is in the air around you and adjust your settings to compensate for that reduction in intensity.
Although you’ve given your camera time to acclimatise outside its case so that its internal temperature matches that of the temperature outside it, you still need to adjust the camera settings to take that outside temperature into account.
Reflected apparent temperature
When operating a thermal imaging camera to measure the temperature of a specific object, you’ll need to calculate the amount of energy your target is reflecting. Then you’ll need to deduct that amount from the value of the total energy your camera’s picking up through its lens (we talk about this in more detail in our Knowledge Base article “What is reflected apparent temperature”).
Those settings we’ve just looked at can be adjusted after the image has been captured – either with the camera’s own software, or once that image has been downloaded onto a computer. But since it’s impossible to make any changes to the following elements after capturing an image, it’s essential to get these right beforehand:
Some camera models do have an autofocus feature, but it’s not advisable to depend on it, especially since focus is perhaps the most important consideration when operating a thermal imaging camera. Captured images which aren’t correctly focussed won’t be able to show small differences in thermal energy between adjacent areas properly, so it’s very possible you won’t identify a problem which would otherwise have shown up. Because you’ll need to focus slowly due to the speed of your camera’s imaging system, it may take some time to get the best focus for an image … but that time will have been very well spent.
Many thermal cameras have pre-sets for different temperature ranges – the most common would be from -40° C to 120° C, 0° C to 500° C and 300° C to 1000° C, so you need to select the most appropriate range setting.
If you’re capturing the image of a wide area, it’s essential to get as much of that area as possible into that image. But if your target is a small area or object, you’ll need to get as close to it as possible because of the way a thermal camera’s detector array is laid out. Simply put, your camera’s not just recording the temperature of a single pixel in that array, but also that of the eight pixels surrounding it – so the closer the camera is to that target, the better. (Don’t rely on your camera’s zoom option because it’s just a digital function, meaning you’ll be losing a lot of the resolution you need in your image.)
There are other considerations, such as the question of the most appropriate angle from which to capture the best image and, of course, climactic conditions if you’re working outdoors.
But once the options and settings described above are in place, you’re then in a position to create accurate images which you can use to analyse your client’s problem and offer a solution.
If you’re interested in a career in any kind of thermal imaging, you’ll need the right kind of training to gain the qualifications and certifications necessary for that career.
And after taking any of the many specialist thermal imaging courses available from the iRed Academy, you’ll know how exactly to approach a problem situation, how to set up your thermal imaging equipment, how to analyse the image produced and how to explain that analysis to provide the solution to that problem.
Talk to us about the thermography career you’re interested in, and we’ll help get you started, get trained, and get qualified.