1. A computer-implemented method, comprising: performing, by one or more computing devices: estimating, from image content of a captured image, a value for a parameter to be used in a digital image processing technique when applied to the captured image; obtaining, from metadata corresponding to the captured image, a value for the parameter determined when capturing the captured image; determining that a difference between the estimated value for the parameter and the value for the parameter obtained from the metadata exceeds a threshold; and applying the digital image processing technique to the captured image to generate an output image, the value for the parameter obtained from the metadata used in the digital image processing technique instead of the estimated value in response to said determining that the difference exceeds the threshold.