Abstract: The same physical scene seen in bright sunlight and in dusky conditions does not appear identical to the human eye. Similarly, images shown on an 8000 cd/m2 high-dynamic-range (HDR) display and in a 50 cd/m2 peak luminance cinema screen also differ significantly in their appearance. We propose a luminance retargeting method that alters the perceived contrast and colors of an image to match the appearance under different luminance levels. The method relies on psychophysical models of matching contrast, models of rod-contribution to vision, and our own measurements. The retargeting involves finding an optimal tone-curve, spatial contrast processing, and modeling of hue and saturation shifts. This lets us reliably simulate night vision in bright conditions, or compensate for a bright image shown on a darker display so that it reveals details and colors that would otherwise be invisible.