The hardware solutions to stealing a few extra bits of luminance control are really only possible with CRT type displays as even the most accomplished home engineer will have trouble fiddling with a laser printer. The most common hardware-based scheme is used with monochrome displays when one has the benefit of colour-capable display hardware. Assuming that the outputs are already 8 bits then the theory is this: take the green output, divide it by 256 and add it to the red output using the combined signal to drive the monochrome monitor. In this way, the levels generated by the green signal will fit nicely between those from the red output giving 256x256=65536 distinct levels or the equivalent of 16 bit luminance control. Unsurprisingly anybody expecting to achieve this type of improvement may well be disappointed but a very useful gain can be made this way. The principal problem is that the video DACs found on graphics cards are only accurate to 0.5LSB. This means the output levels may by as much as one part in 512 from their ideal level. Resistors for the dividing circuit aren't available in exactly the required values with the necessary precision either. And what’s more it is very difficult to build a circuit that works well at video frequencies of over 100MHz. And if that’s not enough, who has a monochrome monitor anymore? Nevertheless 12 bits can be obtained using a technique like this.

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