Thought I’d share the solution to what was a frustration as well as a learning curve for me. I have been trying to engrave a dither image for a while now. Every time I created the gcode in LW, it left out almost all of the pixels except for the pixels in groups. Well, I finally tried some of the settings in the raster operation. The one that gave me the best results was the brightness setting. I set it to -1 and LW showed all of my dithered image pixels. At 0, it will only show the large groups of pixels. After I did that, I attempted a couple of comparison engravings that I would like to do on granite, but this is on wood as a test. We recently put our dog to sleep, so we would like to make a granite memorabilia of him. In the photos I did two engravings. each had a grayscale and dither version of the same photo. The two tests differed in the speed/power settings only. I think the top right looks the best. Albeit, this will probably look much different on granite. More tests to follow, but I am glad I figured out how to get all of the dither image pixels included in the gcode!
Top right does indeed look very clear. Although you may find Bottom right works better on the stone due to higher power/lower speed. Keep us updated with the progress 
I have found the need to dither images now in LW4 that I previously have not had to do in LW3 +Peter van der Walt can we get an “experimental” option in LW4 to use the dark and light speed compensations again? It doesn’t need to be active all the time, but only when a user wishes to use it like the trim pixel, join pixel, and burn white options
@Arion_McCartney hit that bottom right image with some 400 or 500 grit sandpaper selectively and you will find it’s still a usable engrave. Not much pressure is needed for it
+Peter van der Walt looks like I will need to do some comparison gray scale engraves between LW3 and LW4… And I’m pretty sure I was 20$ of that donation to @Sebastien_Mischler I will try to get things going to raise more, grayscales are my favorite
If someone puts a fundraiser here for grayscaling improvements, I’ll put some cash in!.. Can’t do much, but I can spare a few bucks here and there to support the project!
I am crossing my fingers in hopes that there will someday be a C3D GRBL version created. The more I raster engrave the more I feel inhibited by smoothie. Vector engraves are great, not so much with raster. I mean, it is definitely doable, but I feel there could be more consistent results with GRBL while not having to worry about stuttering 
what are the options for getting GRBL in a k40? Wiring in a GRBL board seems the only choice right now as far as I know? The top engravings in my photo are done at 40mm/s and had stuttering where the laser head would stop many times in one pass.
Drawback is that all settings are compiled in… No USB SD card access anymore either
+Peter van der Walt I tried. Only to realize that the C3D board is not yet working with GRBL-LPC… https://plus.google.com/101442607030198502072/posts/G9q5ois38RF
+Peter van der Walt it looks like it locks up for everyone who tries it on a C3D. Something seems to be different about that board.
+Peter van der Walt i was working with Todd Flemming who was gracious enough to help me out, but I was ultimately unsuccessful. Toward the bottom of that thread you can see my progress. I asked ray Ray Kgolodovsky if he has ever had it running on a c3d board and he said someone else tried to test it but was unsuccessful as well. He has not had the chance to test it. Also in that thread. I wish I knew how to get it to work. Spent many hours this last weekend trying.