An image sensor system, comprising: a matrix having rows and columns of photo-sensitive pixels , wherein pixels that are arranged in the same column are configured to output an output signal onto a column bus for that column if such pixel is selected for read out; a conversion unit for converting a pixel signal that is based on one or more output signals for a given pixel into a respective digital number, said conversion unit comprising a global ramp unit configured for generating a ramp signal, the conversion unit further comprising, for each column of pixels: a comparator for comparing the relevant pixel signal to the ramp signal; a binary counter configured for increasing a binary count value in dependence of a clock signal and a result of said comparing; a controller for resetting each binary counter to an initial value at the start of a conversion cycle; a binary count value collecting unit for collecting the binary count values from each binary counter; characterized in that the columns of pixels are grouped in a plurality of pixel column groups, each pixel column group comprising at least three columns of pixels, wherein the controller is configured to reset the binary counters corresponding to the pixel columns in a pixel column group at the start of a conversion cycle such that at least three pixel columns among the at least three pixel columns in a pixel column group are reset to a different initial value, wherein the controller is configured to set, as initial value for an m th pixel column in a pixel column group, the m th lowest digital number to be outputted by the binary counter associated with that pixel column. a matrix having rows and columns of photo-sensitive pixels , wherein pixels that are arranged in the same column are configured to output an output signal onto a column bus for that column if such pixel is selected for read out; a conversion unit for converting a pixel signal that is based on one or more output signals for a given pixel into a respective digital number, said conversion unit comprising a global ramp unit configured for generating a ramp signal, the conversion unit further comprising, for each column of pixels: a comparator for comparing the relevant pixel signal to the ramp signal; a binary counter configured for increasing a binary count value in dependence of a clock signal and a result of said comparing; a comparator for comparing the relevant pixel signal to the ramp signal; a binary counter configured for increasing a binary count value in dependence of a clock signal and a result of said comparing; a controller for resetting each binary counter to an initial value at the start of a conversion cycle; a binary count value collecting unit for collecting the binary count values from each binary counter; characterized in that the columns of pixels are grouped in a plurality of pixel column groups, each pixel column group comprising at least three columns of pixels, wherein the controller is configured to reset the binary counters corresponding to the pixel columns in a pixel column group at the start of a conversion cycle such that at least three pixel columns among the at least three pixel columns in a pixel column group are reset to a different initial value, wherein the controller is configured to set, as initial value for an m th pixel column in a pixel column group, the m th lowest digital number to be outputted by the binary counter associated with that pixel column. <EOS>