Formats for engraving photos.

[Jeffrey Dewing]

I have a brand new Trotec, Speedy 300, 80 Watt. I'm trying to engrave photos on marble and granite. I'm getting good results but my problem is getting rid of the back ground. I can get it to go away, but when I turn the photo into a negative It engraves my material all the way down the photo. Can anyone help me get the background to completely go away./ I have Corel 7 and go into photo paint, remove the background, do all the other necessary steps, and when I reverse the image the background goes black! The same thing happens when I try to engrave on glass. If I want to engrave a drinking glass, I just want the person or subject matter to engrave, not the entire pallet. When someone tells me what I'm doing wrong I'll most likely feel kinda stupid but at the moment I could really use some pointers.... Thanks Jeff from Nor'Easter Laser...
:confused:

[Glen Monaghan]

When you say that you get the background to go away, I'm guessing you are filling/painting it white. Then, when you create the negative image, the white background turns black, and that's causing the machine to engrave from top to bottom and left to right, the entire length and width of the picture.

You could fill the background with black rather than white prior to creating the negative or, after creating the negative, select the now-black background and make it white.

But, the better solution is to actually eliminate the background, deleting it and saving in a format that supports transparency, such as png (definitely NOT jpg or bmp). That way, the background isn't affected by subsequent processing (such as the negative transformation), doesn't engrave, and the image can easily be composited with other graphic elements if desired (for example, you could paste it over some other image/background/texture).

[Keith Colson]

Hi Jeffrey, I am no expert but I can share the process I did for the last job I did which came out great seen here..
http://www.sawmillcreek.org/showthread.php?226104-Photo-engraving-granite-using-Corel-and-VLS6-60

This video helped me a lot, note that if you remove the background it is quite often good to add a halo so the outline remains defined. There is a second video on that channel that was good too.
https://www.youtube.com/watch?v=jfy6iqFVmSc&list=PLo-D6BvmUiCHyc9FIIstZ9jPBST3x8mWK&index=1

My process for my last image on black granite was as follows.

1) Size mm to fit work peice
2) Convert to 8 bit greyscale
3) Bitmap Resample 300 dpi
4) Bitmap auto adjust
5) Bitmap sharpen Unsharp mask 500% Radius 10
6) Effects Adjust Tone curve - Set the max value to 26 - 36 or so.
7) Effects Transform Invert
8) Print error diffusion on, Power 100 x 50, Density 3. This step could be convert to 1 bit stucki instead.
9) Wipe Amor All on granite
10) Focus and run

I did do a couple of tests using a really small version of the picture to tune the brightness

Cheers
Keith

[Scott Shepherd]

My process for my last image on black granite was as follows.

1) Size mm to fit work peice
2) Convert to 8 bit greyscale
3) Bitmap Resample 300 dpi
4) Bitmap auto adjust
5) Bitmap sharpen Unsharp mask 500% Radius 10
6) Effects Adjust Tone curve - Set the max value to 26 - 36 or so.
7) Effects Transform Invert
8) Print error diffusion on, Power 100 x 50, Density 3. This step could be convert to 1 bit stucki instead.
9) Wipe Amor All on granite
10) Focus and run

I did do a couple of tests using a really small version of the picture to tune the brightness

Cheers
Keith

He doesn't need to do all that, his Trotec has a built in Photo Mode that does an excellent job.

[Don Corbeil]

Yes, the trotec JC has built in dithering options in either ordered, stucki, jarvis, or floyd steinberg. I haven't played around with these much, since I primarily use photograv, but I do wonder which dithering pattern tends to give good results. I think the stucki dithering seems to be closest to what photograv uses.

[Jeffrey Dewing]

Thank you all for your input! I think the problem I was having was in the format... jpg keep the background, I think, so I need to switch over to a png so that when I go into photo paint and remove the background It really goes away. Thanks again for all of your help...

[Dee Gallo]

This may be weird, but when I do this kind of work, I prep the greyscale and at the end I fill the whole background with black. Then, when you invert, the whole background is white. Any stray pixels show up as little black dots, so they are easy to erase after inverting.

If you color the whole background white or erase the whole background, you still end up with lots of grey spots you can't see until it's too late.

cheers, dee

[Jeffrey Dewing]

Hi Dee! Coloring the background black is what I'm doing now. When I'm in corel I put a box the size of my pallet there and fill it with black, then put my photo on top. When inverted it seems to work well... Thanks Dee!

[Ray Scott]

Wen you are doing photos... Nothing beats PhotoGrav. I still combine software methods to remove the background, masking, re sampling..etc.

[Scott Shepherd]

Wen you are doing photos... Nothing beats PhotoGrav. I still combine software methods to remove the background, masking, re sampling..etc.

I'd disagree with that comment. I owned it and it was far too time consuming to master. Have you used the Photo tools from Universal or Trotec? One click, done. Awesome results.