A method of estimating light output of a lamp in a scanner prior to the lamp being fully warmed-up. The method includes measuring a spectral characteristic of light emitted by a lamp in a scanner at a time t0 prior to the lamp being fully warmed-up and estimating the light output of the lamp at a time t1 based on the measured spectral characteristic, wherein t1 is greater than t0. A method of scanning, as well as a scanning apparatus is also provided.