I wonder is there a way to restrict luminance output to a range of a monitor's total output capability? I need to reduce the luminance of all monitor output in an experiment to operate within the bottom 10% of the total monitor's capacity, i.e. as if I had just turned the brightness down to 10% (unfortunately, just turning down the brightness is not an option). In other words, I need a global reduction in luminance of 90%. My blacks should be the same as before, whites will be 10% of total monitor output, and 'grey' would be in the middle. The monitor is properly calibrated already. I know that I could manually adjust all my stimuli pixel values to simulate this, but I wonder if there is a built-in function in PTB (perhaps at the time of Screen('OpenWindow')?) that just applies a global luminance transformation in this way?
I note the function Screen('ColorRange'), but this looks to *clamp* colours ourside of a specific range. I don't think this is what I'm trying to achieve, as I wish to globally affect all luminance values sent to the monitor. Furthermore, I don't think it would be appropriate to use Screen('LoadNormalizedGammaTable'), since the monitor is already gamma corrected, and what I need is a global 90% reduction to *all* luminance values output, rather than a nuanced curve.