Proper color management would solve this problem, but if your boss is asking you do do that, I’m assuming that isn’t possible where you work.
You can take the request literally by using curves. Pull the 50% point down to 45%, 40%, 35%, etc. Lower numbers = brighter image.
Carl.
Another easy way is to make a duplicate layer set to screen mode, then vary opacity.
Allen:
Try a blank adjustment layer instead of duplicating the image layer (i.e., create a new adjustment layer: levels, curves, etc and make no adjustment; just hit ok). Then screen/multiply/etc the adjustment layer.
J