The vagaries of Dither

LightBurn Software Questions
1

I recently completed a project to make a guitar pickguard and I would like to make another one. However, when I went to do it I could not get the same result. This is best illustrated with a picture:

guitar
guitar1920×1441 271 KB

A close look at the pickguard, which is made using 2 ply acrylic, shows a faux metal effect done using linear shading. The graphics were created in Inkscape and Imported to Lightburn. The challenge is getting the shading to work consistently. The photo shows that it can be done. However, sometimes I can get it to show and burn correctly, and sometimes I can’t. I settled on the Stucki dither since it gave the best result. The shading is an image, which gets converted to a bitmap in Lightburn. When I use Adjust Image sometimes it shows the shading correctly, and sometimes not: see Lightburn file:
stucki.lbrn2 (717.5 KB)
The file contains 2 images, one which shows correctly in Adjust Image, and one not. I cannot figure out why they are different, since they both came from the same source in Inkscape. When I successfully made the Pickguard, it also showed correctly in Preview. Now even the version that is correct does not show correctly in Preview. Hoping that somebody can enlighten me about the vagaries of using the same dither on different images. BTW all images, good or bad, show the dither shading in the Cut Settings Editor.

2

The speed and power for those two images are different, which will definitely affect the results:

Fill Cut Settings
Fill Cut Settings1046×950 119 KB

Edit to add: The left image has an outline that changes the scanning path.

Probably critical: the right image has both Min and Max power set to 20%, so the controller cannot vary the power.

That doesn’t seem to be the case, as the right image has a much higher pattern density.

The left image is 3472×2678 and the right is only 1307×993. This will affect how the Stuki dither works, because the right image must be upscaled by a factor of three to get the final result: it starts with less detail than the left image.

I think the problem lies upstream of LightBurn.

Inkscape is a vector graphics program that you’re using to produce a raster image. If you arrange the exports to produce the same number of pixels in the raster files (PNG, whatever), import them into LightBurn, and apply the same layer settings, then (I think) LightBurn will produce the same results.

For image processing, however, I think you’d be better off using a raster graphics program (like, for example, GIMP) that produces an image file with known properties.

3

Mis-read the machine type :poop:

:smile_cat: