The Importance of Focus and Infrared Imaging

Joseph DeMonte | Director - Technical Training & Support, ABM Franchising Company

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  The Importance of Focus and Infrared Imaging

  First, let’s discuss the focus on your infrared camera. Some lower-resolution infrared cameras will come from the factory using a fixed focus only. What this means is that the camera will not need to be adjusted for focus and will be in focus without user input. However, a fixed-focus camera can be out of focus if the camera itself is placed too close to the object that is being viewed by the camera. Typically, most infrared cameras with the standard lenses offered by the manufacturer will reach their minimum focus distance when they are closer than about one foot, or one-third of a meter, to the target. It will vary from camera to camera, so it’s always best to try it out for yourself and see when the focus can no longer be maintained. If the camera has a higher resolution, the manufacturer will rely on a manual- or an automatic-focus feature. It will still have a minimum focus distance, so keep that in mind.

  Why focus? Infrared images, once captured or saved, can allow a qualified thermographer to make further adjustments to the image with computer software or by recalling the image on the camera. Focus, however, cannot be adjusted after an image has been captured or saved. Consider the two images of a lit candle that are shown here. With the image on top out of focus and the bottom image in focus, temperatures measured are nearly 400°F lower on the out-of-focus image than the focused image. If an image of a hot electrical connection with a cool background is even slightly out of focus, the temperatures will be lower than the actual. Once the image is saved, no further corrections to focus can be made. In order to perform an accurate infrared survey, proper focus is a key parameter to consider.

Tags: ABM, infrared, Joe DeMonte

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