You can't define more than 8. The API allows only 3 bit input. I also tinkered with the lookup table, and was able to create a lot of different gray shades, but

You can't define more than 8. The API allows only 3 bit input. I also tinkered with the lookup table, and was able to create a lot of different gray shades, but I was not able to produce ~40-60% gray.