Variable Power Grayscale Engraving?

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#1

In testing, ive noticed that grayscale engraves seem to be dithering images rather than outputting different levels of power. It causes a more texturized/grainy look on materials and not smooth transitions. Is there a certain method that should be used for making the laser do a variable power constant engrave instead of it just dithering the image? @dan


#2

How would what you’re describing be different from 3D engraving? I mean, wouldn’t more power for darker engraving simply translate to deeper as well? Or would it also vary speed to make it flatter as well as darker?


#3

Maybe after they release the 3D this could be fixed :thinking:


#4

Doesn’t the GF only handle 256 power levels? It will be hard to get a perfectly smooth gradient with only 256 colors. Plus the material can have a big impact on that.
Have you tried converting your image to a 256 grayscale image first to try and control the image quality a bit. It sounds like however they are converting the image may not be perfect yet.

Edit: Now that i think about this more you should have a smooth gradient with 256 levels. I confused 8-bit(256 colors) with 6-bit(64colors) in my head. I used to have convert a lot of images to 6-bit for some old newspaper software so we always where battling dithering.

Not sure what the issues is then, maybe it is just the material then.


#5

Not sure why you’re postulating 256 levels can’t be smooth.

Looks pretty smooth to me. I’m not saying it’s the smoothest thing in the universe, but I would still say that “smooth” is a correct word to describe the transition.

Never mind, then. :slight_smile:


#6

Yeah. I always convert color images to grayscale first to make sure I have the color balance correct.

Here is the standard gradient engrave I do on any new materials (you’ll see one or two vector power level engraves in there too)


#7

Ya i just edited my original post because in my head i confused 8-bit and 6-bit. There is a big difference there. :slight_smile:


#8

It’s not material. Every raster image seems to be passed through a Floyd-Steinberg dithering algorithm. This could be specified in the glowforge backend on a per material basis, but I haven’t found one that I have that this does not apply to.

I’d really like to be able to try it without that dithering to see if the engraves come out higher quality. A flat background would be really nice


#9

Wow that is weird. Its not even a constant dithering. What is the difference between the top and bottom of each material?


#10

Some materials I leave the masking on to provide extra contrast. This gives me an idea of how it will look with and without the masking.


#11

You are incredibly diligent and thorough to do 1%, 100% and multiple lpi’s across several materials.

Thank you.


#12

You can’t specify which algorithm to use? Sometimes the alternatives like Stucki, etc are better depending on the material you’re engraving and the picture you’re doing. If they’re going to dither vs variable power then I’d like to be able to alter the dithering algorithm used to better tune the results.


#13

No, currently it’s baked in. I don’t mind the dithering in photographs, but in more technical pieces I would like to not use it. Having a choice to select between many would be ideal, or even none and I can just do it before importing the image.


#14

I’ve found that the Pink-Floyd-Steinberg algorithm tends to be a little on the Dark Side (of the Moon, for you youngsters)


#15

:smile: Sir, you have made my day.


#16

It’s just another brick in the wall.


#17

I’d prefer this. Dithering needs to be performed in the application of choice. I mean, how can you tell what your result will be if you can’t see it beforehand?

I’m a little surprised you’re seeing Floyd-Steinberg dithering. I’ve seen halftoning in many laser images. I wonder what’s really happening here.

@GlowforgeStaff Can we get some clarification on what’s happening here with the dithering and what we can expect in production? Thanks!


#18

I agree and disagree on this. The whole purpose of proofgrade is to make life easy, especially for those who dont have the experience to set up an image to look good in a laser. There should still be an ‘automatic’ setting for those who would like it, and Ill definitely use it instead of going through all the steps to dither things myself. (which was my least favorite part of the process).

BUT, I would like to be able to turn this off when I need to. Its already there, no reason to remove it. Just put a switch in and maybe an option to default to either on or off.


#19

Nice job of organization–all those beautiful test engrave panels!

It would be a shame if GF pushed a silent update to your machine that made them all worthless for reference purposes…


#20

Is this only on your own materials or on proofgrade that you are seeing the dithering?

Pure speculation ahead.

How are you converting to grayscale? Isn’t there a reduce color set to 8 bits of black to white and a set all rgb values to even conversion that technically leaves it a color image?