A method of and a device for characterizing a light source and a method of selecting a replacement light source are provided. The method obtains (102) a first image of a light source in operation, obtains (106) a second image of the illuminated environment, and obtains (104, 108) first camera settings and second camera settings of the optical system and image processing system of the respective first and second camera at the respective moments in time that the first image and the second image was obtained. The first image, the second image, and the first and second camera settings are analyzed (110) to estimate characteristics of the light source. The characteristics of the light source may be used to propose a replacement light source and characteristics of the proposed replacement light source may be used to simulate the effect of the replacement light source on the illuminated environment.