Laser Engraving Grey scale images

[Jim Coffee]

Good evening group:

Occasionally there are posts to the effect of "I cannot engrave this photograph...what's wrong?" I have wanted to post a response but have not had the time to post what I have wanted to say. I have the time now.

From my perspective there are two major components of printing a grey scale image.

1. What are the combination of the engraver and the material capable of?
2. What is the image that is trying to be engraved.

This post will deal only with the first item...what are the combination of the engraver and the material capable of?

As a photographer and a printer of Black and White images I've learned that the combination of the printer and the paper needed to be understood. To do this test targets are printed. Sometimes profiles are created, etc.

It is the same concept for laser engraving (except a bit more frustrating and tedious)

Search Google images for "grey scale test chart" or something similar. You will be offered many test charts. What you are looking for is something that at least contains a grey scale ramp...steps from black through white. Here is a link to one.

You can see that the target that I use also contains an image of a woman wearing a hat, and some resolution tests. I just looked for this particular test target (the one that I use) and do not see it available...however not important. Choose one that you think you will be comfortable working with and that you can download in a high resolution.

As you can see I've laid my test target out in such a manner that I can date the test, and can include machine settings. The set that you see are a couple of the ones that I engraved right after I replaced my tube. I will keep them as a benchmark of the condition of the machine when I replaced the tube.

Note that the grey scale prints differently with the different settings. It's hard to tell from this small Internet image...I actually use a loupe on the real thing. A lot can be learned by engraving a good test target.

Bottom line...if you cannot successfully engrave a reasonable grey scale with your engraver/material combination...you will not be able to engrave a grey scale image either.

[Chris Tatarian]

Hi Jim,

Very insightful and great idea for organization.

Thanks,

Chris Tatarian

[Dan Hintz]

Factoid: That woman is Lena Söderberg (listed Lenna Sjööblom as in the issue)... she was a Playboy Playmate in the november '72 issue, and her image (the clean part of it, anyway) is used as a test subject in a number of imaging algorithm tests (MPEG, JPEG, etc.). I have the original, uncut image (NSFW), and I've been trying to get a hold of that month of Playboy for posterity (my thesis research was in imaging). It's used because it contains a wide range of suitable tests in one image, from a wide range of colors (particularly skin tones) to a wide range of detail (from smooth gradations on her skin to sharp changes in the feather on her hat).

[Chuck Stone]

Factoid: That woman is Lena Söderberg (listed Lenna Sjööblom as in the issue)... she was a Playboy Playmate in the november '72 issue, and her image (the clean part of it, anyway) is used as a test subject in a number of imaging algorithm tests (MPEG, JPEG, etc.). I have the original, uncut image (NSFW), and I've been trying to get a hold of that month of Playboy for posterity

Not surprising, Playboy had once said it was there best selling issue of all
time. Probably just us photo buffs trying to get technically proficient.
That image is also purported to be the first jpeg, but I don't know how
true that is.

[Martin Boekers]

Good work Jim,

I come from a commercial photographic printing background and multiple daily
tests were required to keep our lines in control, I have fiddled with this a bit
with the laser, but as with the rest of us, it gets hard to find the time to
refine the ideas.

I have talked with Epilog suggesting that they come up with test images
such as this, as it would be a great benefit to to all of us, not just the
ones starting out.

I have also suggested that they come up with a test file set that helps
in diagnosing laser issues. When I have called with issues in the past
they usually run me through a battery of tests to help diagnose the
orgin of the problem. It just seems to be a natural progression to have
a standard file(s) that help with diagnostics.

If they don't eventually come up with a system, someone I'm sure will realize
that if they set up a package to help in finding optimum settings
for any material they probably can make some good money with it.

I think it could be worth $50 - $100 just in time saved with testing
and optimizing your settings.


Are you laser manufactures listening?


Marty

[Don Gares]

Factoid: I've been trying to get a hold of that month of Playboy for posterity (my thesis research was in imaging).

Just point you browser to tinyurl.com/25uqbav and you will find it on e-bay for $15.00 plus some shipping.

Don

[Doug Griffith]

Good work Jim,

I come from a commercial photographic printing background and multiple daily
tests were required to keep our lines in control, I have fiddled with this a bit
with the laser, but as with the rest of us, it gets hard to find the time to
refine the ideas.

I have talked with Epilog suggesting that they come up with test images
such as this, as it would be a great benefit to to all of us, not just the
ones starting out.

I have also suggested that they come up with a test file set that helps
in diagnosing laser issues. When I have called with issues in the past
they usually run me through a battery of tests to help diagnose the
orgin of the problem. It just seems to be a natural progression to have
a standard file(s) that help with diagnostics.

If they don't eventually come up with a system, someone I'm sure will realize
that if they set up a package to help in finding optimum settings
for any material they probably can make some good money with it.

I think it could be worth $50 - $100 just in time saved with testing
and optimizing your settings.


Are you laser manufactures listening?


Marty

Not only image files but corresponding colormap setting files covering a wide range of speed/power/frequencies.

I use a template file with 16 color squares outside the work area. I then load colormap settings that correspond to the colors. From there I use the eyedropper and apply the color to images within the work area. By always using the same color palette, I can easily load different settings files.

I also keep several test files with the same image and vector cut line repeated 16 times. Each uses a different color from the pallet. I use these to test new materials. This makes finding the optimum settings fairly quick.

[Martin Boekers]

Great work Doug!

It makes "dialing in" so much easier and consistant.

As I said, you would think after all these years making lasers
at least one manufacture would have developed such a system
to include with your purchase.

Also a test file could be used as a "benchmark" to burn from time
to time to see how your process or tube is holding up.

Marty

[Dan Hintz]

Another (unfortunate) factoid: Lena hasn't aged well, unfortunately.

[Mike Null]

Ahhh! But she was certainly remarkable in her day.

[Michael Kowalczyk]

So who will be the first to post a CDR file we can use to make a master for each type of laser?

I will be happy to convert one for Trotec users if someone will post a master we could use.




Maybe we should ask that the final masters for each laser be posted in CDR X5 so everyone would have to update to the current version














Just kidding






But if you want to be on the cutting edge of technology, you've got to be current.

[Bill Cunningham]

Factoid: That woman is Lena Söderberg (listed Lenna Sjööblom as in the issue)... she was a Playboy Playmate in the november '72 issue, and her image (the clean part of it, anyway) is used as a test subject in a number of imaging algorithm tests (MPEG, JPEG, etc.). I have the original, uncut image (NSFW), and I've been trying to get a hold of that month of Playboy for posterity (my thesis research was in imaging). It's used because it contains a wide range of suitable tests in one image, from a wide range of colors (particularly skin tones) to a wide range of detail (from smooth gradations on her skin to sharp changes in the feather on her hat).

There... I just hadda do it... A Google Image search of course..

[Dan Hintz]

The "clean" portion of the image we use in academia for testing purposes:


I paid special attention to the feather area because my research area was in wavelet-based compression (or that was at least a part of it), and wavelets do a significantly better job at handling high-frequency areas.

[Gary Hair]

I paid special attention to the feather area

The area I would pay "special attention" to would be south of the feathers...

[Lee DeRaud]

I paid special attention to the feather area because my research area was in wavelet-based compression (or that was at least a part of it), and wavelets do a significantly better job at handling high-frequency areas.

I took a look at a full high-resolution copy of the picture, and for the life of me I can't figure out how to distinguish between goosebumps and compression artifacts.

Further research is obviously required.