there are so many variables, like feed-rates, step overs, tool call out, size of the burning beam, size of the image your engraving, how the image is processed or enhanced, where you set zero based on the power of your laser, full watts of the laser and the type of wood your engraving on.
I received my laser power meter yesterday and now I should be able to focus the lens somewhat better then before based on it's maximum wattage output power. Before I was trying to focus it down (the best I could visibly see) to the smallest dot possible on a black anodized piece of aluminum. I can only assume the smaller the dot, the more full watts, detail and intensity you will be able to get out of the laser. Also it should be more responsive to the change in the inputted voltages to the analog modulation to visibly see the difference in shades too.
I believe the best way to do the grey-scale test with my laser and with the PVC software is, redo the 256 color pallet again with more refinements and I will post the results later today. I will scan in the image and post it instead of taking a picture so it does not loose as much detail.
Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver