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How does a neutral density filter affect the scene dynamic range of FLIR’s OEM cameras?

Scene dynamic range is inversely proportional to the transmission loss introduced by a neutral density (ND) filter.

For FLIR’s standard OEM cameras:


High Gain Mode

Low Gain Mode     

Tau2 640, 324     

-25 °C to +135 °C 

-40 °C to +550 °C

Tau2 336

-25 °C to +100 °C

-40 °C to +550 °C


-40 °C to +160 °C

Not Available


  50 °C above and below ambient temperature   


0 °C to +120 °C

0 °C to +450 °C*


to 140 °C

to 500 °C

*Lepton radiometric, only.

Introducing an ND filter with X transmission will increase the scene dynamic range by a factor of 1/X, assuming that the photon contribution coming from the filter itself is negligible.

For example, with a 0.65 ND filter, a Tau2 640 could potentially see up to 550 °C/0.65 = 850 °C in Low-Gain mode.