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The Importance of Imager Frame Rate
Tip written by: Infraspection Institute

Experienced thermographers know that image clarity is one of the most important considerations in thermal imaging. For thermal imagers, imager frame rate is an important characteristic that can greatly influence image quality.

Frame rate or frequency describes the rate at which an imaging device produces unique consecutive images or frames per unit of time. Until recently, most NTSC compatible thermal imagers produced 30 to 60 video frames per second. This frequency provided imagery that was considered ‘real-time’.

Thermal imagers that have real-time frame rates permit imaging of either slow moving targets or imaging of targets while the imager is in motion. Examples include infrared inspections where the imager is panned across the face of large targets such as buildings or where the imager is hand carried such as during walkover inspections of a flat roof.

For a variety of reasons, many modern imagers are now manufactured with frame rates of less than 30 frames per second. When using an imager that produces less than 30 frames per second, a thermographer will notice ‘ghost trails’ or image smearing should either the imager or target be in motion. This condition will worsen as lower frame rates are encountered.

Clear imagery is possible with imagers having a slow frame rate; however, both the target and imager must remain motionless in order to eliminate image smearing. For some imagers, it may take several seconds for the image to become clear. Because of this, slow frame rate imagers may not be suitable for inspecting expansive targets or targets that are constantly in motion.

Because frame rate cannot be changed for any imager, this feature must be considered at the time of imager selection and/or purchase. Prior to purchasing any new thermal imager, be certain to try the equipment under the same conditions that you will likely encounter in the future to ensure that the frame rate is adequate.

Equipment selection and use are two of the many topics covered in the
Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training including course locations and dates, visit us online at www.infraspection.com or call us at 609-239-4788.