Engraving on Slate - Missing Pixels

Hi, I am trying to engrave on a slate coaster with my Creality Falcon2 40W. I have done a material test to try and narrow in on the speed/power, and have been tweaking the image settings, but the image engraved on the coaster is not close to what is shown in the Adjust Image window of LightBurn. Basically, it looks like there are a lot of pixels that don’t end up getting engraved on the coaster.

Hopefully, someone can tell me what I am missing and point me in the right direction.

My settings are:
6000 mm/min, 30% power
254 DPI, Line Interval 0.1
Dot Width Correction - ON, set to .08
Image Mode - Jarvis, Negative Image
Contrast 10, Brightness 0, Gamma 1

The original image was given a Posterize filter and changed to grayscale before importing into LightBurn.

In the photos, there is the original, the dithered version in LightBurn, and then what the slate looks like. The missing pixels are very apparent in the case of the front leg, there are pixels that form a line for the leg, and then sporadic pixels in the leg itself. I didn’t take a picture of the slate in this area, but on the slate, pretty much none of those pixels are engraved at all.



I’ve found slate has a non-linear response. For me, dark shades can be separated by as little as .50 percent change in power.

I haven’t worked with photo engraving yet, so I’m not sure how that applies to photo settings.

Notice the power steps in this test grid…

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