About Convert to Dots vs Vary Power


#1

When I upload an image which is basically solid colors, then choose Engrave/HD Graphics, I wonder what this choice is? GRAYSCALE, so far I have not seen a use for pattern, but ‘Convert to Dots’ vs ‘Vary Power’, since it is not dimmed out on an image that is color, what is the meaning of this choice? I’ve tested both and it seems to look better as ‘Vary Power’ even without using the slider. Does it have way more effect on a grayscale image vs color?
Thanks,
R.L. Hamm


#2

Vary Power will look better in most materials that contrast well. convert to dots and convert to shapes are included for materials that don’t contrast well with varying power.
Personally, while I am glad that they include it, I like to do any dot or shape dithering in a program as it will give you more overall control.


#3

I would hope it converts the colour to its luminance value to make it greyscale before mapping to power or dots. E.g.

Y=0.2126R + 0.7152G + 0.0722B

These values reflect the different sensitivities to colour of the human eye.


#4

To echo this - dots are good for things like slate or aluminum where it’s burned or not burned. I also prefer to do it in an image processing app but with the GF doing it you don’t want to do it and then have them do it on top of your changes.

I’ve thought about doing my own dithering and then using the vary power since it should be binary, it should preserve my pre-processing but I haven’t experimented yet.


#5

That has been my experience.

I convert my grayscale images to bitmap, using a course line-shaped screen to simulate a woodcut appearance. Save that bitmap to a TIFF, then placed in Illustrator for positioning, adding cut lines, etc.


#6

Thanks all, that helps!


#7

I understand rgb values, usually as eg. #ffbe00 or 120,206,55 but I don’t understand what you posted there, can you elaborate on it? Thanks.


#8

Hum, you responded to @palmercr but quoted me, so I’m not sure who you were asking. Oh well, let me try to field this.
It sounds like you understand computer encoding of color and greyscale at least as well or better than myself so I will assume you are not getting the dithering.

See, heres the thing, if we asign power levels to a photo of say 0-99 some materials respond very well to these varying powers and you get a photo engrave that looks great just by varying power to the laser tube.
Other materials do respond so well. These include but I’m sure I’m missing a bunch, painted metal, anodized aluminum, most rocks including slate.
What goes wrong is nothing happens until say power 30, then from there, there is very little difference from 30 to 99 so it becomes impossible to get a good looking photo engrave by varying power.

A way around this it to fool the human eye/brain by averaging a small area and then varying the number of marks in that area. These marks can be dots or most anything else. You lose fidelity but what you lose in fidelity you get back in contrast. This is how photos in the newspaper worked back in the day,


#9

Thanks for your help, all!

@rhgrafix Thanks for asking about this. If you have any other questions, please post a new topic.


#10