Scene dynamic range is inversely proportional to the transmission loss introduced by a neutral density (ND) filter.
For FLIR’s standard OEM cameras:
|Camera||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|
|Quark2||-40 °C to +160 °C||Not Available|
|Muon||50 °C above and below ambient temperature|
|Lepton||0 °C to +120 °C||0 °C to +450 °C*|
|Boson||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.