Grayscale
Hi guy’s
Just wandering if someone could answer a couple of questions I have.
I bought a K40 and tried to engrave a couple of photos with terrible results. The software that came with it just didn’t work for me and after trying k40 whisperer I decided to pop in a mini gerbil 3 and use lightburn.
I figured that the best way to learn about photo engraving was just to try out lots of settings and engrave the same picture on the same material lots. I decided to use paper and if I get close the leap to another material will be smaller. So speed wise I settled on 100mm/sec and power min 1% max between 7.5% and 10%. DPI 304. That does burn through the paper in the very darkest bits but it’s close enough for the moment.
My questions are.
The greyscale pictures are turning out way better than the dithered ones. Is this because the Gerbil is sending more information than the old control board did? Are there settings for this or is it automatic?
All the dithered pictures are pretty poor. The newsprint is probably the best. Is there a way to increase the resolution of the dithering in lightburn?
A little help would be appreciated
Merv
Hi Merv,
This is an excellent question and many beginners bump into this issue. The first thought is to bump up the resolution (DPI) settings. Unfortunately that does not work... we wrote a blog about it which you can find here https://awesome.tech/quality-photo-engraving/
In short, make sure that the beam is in focus. The X shape beam (from the side viewed) can only deliver the best and highest resolution when the middle of the X is on the surface of the engraving work piece. For cutting you want to be deeper (resulting in a slot or kerf). Best is to laser a line at say 50 DPI and examine the dots at various focus points and choose the smallest dots focus setting.
The beam it self gets narrower at lower power, so you get a higher resolution too. The MG does have a higher PWM resolution then the stock controller to allow grayscale (16bits over the full range of 0-18mA). The CO2 laser tube is unfortunately not linear in its output so grayscale can be hard to dial in. You can use the Gamma setting in your photo shop or Lightburn app to compensate for this.
Next is the speed, again laser a line of dots at 50DPI or higher and examine the roundness of the dots. Do this multiple times at various speeds and choose the best dots in terms of roundness/spacing at highest speed or near that maximum.
Now the best! If you engrave at a high DPI, the dots overlap and the picture gets blurred. So lower your DPI to 300, 250, 200, 150 etc and choose the best result. You will see that a lower DPI setting and good contrast/gamma setting/focus delivers stunning results. It is a learning curve and don't rush through it. You spend some hours and plywood but it's worth it. There is a good YouTube video which link is in the blog as well.
Let us know how you went through this process and post photos (before and after).
Enjoy!
Hi Merv,
Greyscale fundamentally has more information than dither, yes.
I always use Greyscale myself, so aren't really an expert in dither. But it sounds like a Lightburn question, so perhaps their forum can help explain what dither settings exist.
Happy to assist further, but I find there's a degree of subjectivity involved. It would be best if you can reply with identical images done in greyscale and dither, pointing out what you like / don't like, and I can help steer you to address the relevant differences.
Regards,
Dan