A computer-implemented method comprising: accessing data from a sequence of images, obtained by an imaging device, of a subject illuminated with ambient lighting and illumination having a sinusoidal intensity modulation in time, wherein the imaging device is configured to operate in rolling shutter mode to obtain, within each image of the sequence, a first spatial portion of the image at a different time to a second, different, spatial portion of the image, wherein a relationship between a frequency of the sinusoidal intensity modulation and a frame rate of the imaging device is such that a different spatial intensity modulation pattern is apparent in consecutive images of the sequence; and determining , based on a set of measured pixel intensity values in each image of the sequence of images, a set of revised pixel intensity values for generating a revised image of the subject by computing, for each pixel of the set, a specified combination of the pixel's measured pixel intensity values from each image of the sequence of images that generates the set of revised pixel values that correspond to a reduced level of ambient lighting and a reduced modulation depth of the spatial intensity modulation pattern being apparent in the revised image compared with the level of ambient lighting and modulation depth of the spatial intensity modulation pattern apparent in at least one image of the sequence of images, wherein the specified combination is based on the combination of the imaging device operating in the rolling shutter mode and the sinusoidal intensity modulation of the illumination resulting, due to a convolution property of harmonic temporal modulation, in each of the pixel's measured pixel intensity values from each image of the sequence of images exhibiting a sinusoidal intensity variation across the sequence of images. accessing data from a sequence of images, obtained by an imaging device, of a subject illuminated with ambient lighting and illumination having a sinusoidal intensity modulation in time, wherein the imaging device is configured to operate in rolling shutter mode to obtain, within each image of the sequence, a first spatial portion of the image at a different time to a second, different, spatial portion of the image, wherein a relationship between a frequency of the sinusoidal intensity modulation and a frame rate of the imaging device is such that a different spatial intensity modulation pattern is apparent in consecutive images of the sequence; and determining , based on a set of measured pixel intensity values in each image of the sequence of images, a set of revised pixel intensity values for generating a revised image of the subject by computing, for each pixel of the set, a specified combination of the pixel's measured pixel intensity values from each image of the sequence of images that generates the set of revised pixel values that correspond to a reduced level of ambient lighting and a reduced modulation depth of the spatial intensity modulation pattern being apparent in the revised image compared with the level of ambient lighting and modulation depth of the spatial intensity modulation pattern apparent in at least one image of the sequence of images, wherein the specified combination is based on the combination of the imaging device operating in the rolling shutter mode and the sinusoidal intensity modulation of the illumination resulting, due to a convolution property of harmonic temporal modulation, in each of the pixel's measured pixel intensity values from each image of the sequence of images exhibiting a sinusoidal intensity variation across the sequence of images. <EOS>