CPC H04N 23/88 (2023.01) [G01J 3/505 (2013.01); H04N 9/67 (2013.01); H04N 9/77 (2013.01); H04N 23/56 (2023.01); H04N 23/71 (2023.01); H04N 23/74 (2023.01)] | 17 Claims |
1. A method of using a camera system to characterize ambient illumination, the camera system having an image sensor to capture a view of a scene, a flash to provide flash illumination of the scene, and a multispectral sensor to capture a spectrum of light from the scene in a plurality of wavelength channels, the method comprising:
capturing a first spectrum of light (DTFA) from the scene using the multispectral sensor whilst the flash is operating to illuminate the scene in addition to ambient illumination;
capturing a second spectrum of light (DTA) from the scene using the multispectral sensor whilst the flash is not operating and the scene is illuminated by the ambient illumination;
determining a difference between the first and second spectra representing a scene flash spectrum (DTF), wherein the scene flash spectrum represents a spectrum of the scene when illuminated by the flash without the ambient illumination;
compensating the scene flash spectrum using a spectrum of the flash illumination (E(λ)) to determine a colour-compensated scene flash spectrum (RT(λ)), wherein the colour-compensated scene flash spectrum represents an average reflectance spectrum of the scene when compensated for the spectrum of the flash illumination; and
processing the second spectrum of light from the scene using the colour-compensated scene flash spectrum to estimate a spectrum of the ambient illumination (RA(λ));
wherein processing the second spectrum of light from the scene using the colour-compensated scene flash spectrum to estimate a spectrum of the ambient illumination comprises dividing a representation of the second spectrum of light (RTA(λ)) by the colour-compensated scene flash spectrum (RT(λ)).
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