If you've just got a new monocular or thermal scope, you've probably noticed something strange: every now and then, the device emits a small "click" sound and the image freezes for a fraction of a second. Don't worry, your equipment isn't faulty; it's performing an FFC (Flat Field Correction).
What is FFC or Flat Field Correction?
FFC (Flat Field Correction) is the internal calibration process used by thermal sensors (microbolometers) to optimize image quality.
Because thermal sensors are extremely sensitive to heat, with continuous use, the sensor's pixels can accumulate small internal temperature variations or "noise." This usually manifests as ghosting, vertical streaks, or a kind of static "haze" that degrades vision. FFC instantly cleans up these imperfections.
Why does it make a "click" sound?
That sound is the device's mechanical shutter momentarily closing in front of the sensor. The software uses that flat, uniform surface of the shutter as a reference to "reset" all pixels to a base value, eliminating accumulated residual noise.
The 3 calibration modes on your equipment
Most leading manufacturers such as Pulsar, Hikmicro, or Infiray allow you to choose how you want this calibration to behave:
- Automatic Mode (A): The device's software decides when calibration is needed based on temperature changes. This is the most convenient mode for beginners, although the "click" can occur at the least opportune moment.
- Semi-Automatic Mode (S): The device notifies you that it needs to calibrate, but you are the one who presses the button to execute it. It's the perfect balance for hunting.
- Manual Mode (M): The mechanical shutter does not close. You must place the lens cap yourself and press the calibration button. This is the preferred mode for professionals who require absolute silence and want to prevent the image from freezing unexpectedly.
Expert Tip:
If you notice that the image from your thermal device starts to show "noise" or streaks, don't wait for automatic mode. Perform a manual calibration (FFC) and you'll see how the image instantly regains its original sharpness and contrast.
Equip yourself with the best
Looking for equipment with silent and efficient calibration management? Explore our selection of professional thermal monoculars and choose the one that best suits your observation or hunting sessions.
Currently, in thermal shooting devices such as scopes and clip-ons, leading brands in this technology, such as ThermTec, Guide, or Nocpix, are bringing back a technology that Dedal thermal devices implemented many years ago. This is called Shutterless (shutterless refresh). This ensures that the equipment does not experience cuts or image freezes at the critical moment of the shot.
Learn more: Discover how NETD influences the need for frequent calibration of a thermal sensor.