In described examples, a method includes: receiving an array of image data pixels for display by a spatial light modulator; dividing the array of image data pixels into a plurality of blocks. For the blocks of the plurality of blocks, the method includes: computing a mean value for pixels in the block; computing a variance for pixels in the block; and, in response to the mean value and the variance, retrieving an indicator of a likelihood of a visible artifact for the block; and in response to the retrieved indicator, outputting a signal to selectively increase or reduce a load time of the spatial light modulator for displaying the array of image data pixels.