Gold method

[Joe Hillmann]

Every once in a while someone mentions trying the gold method. I tried searching for it but all I could find was references to it rather then the post that explained how to do it. Would someone be able to put a link that explains how to do it?

[Dan Hintz]

It's pretty much a point-and-shoot macro... once installed, run it and you'll see.

I'll see if I can dig up the thread...

[Dan Hintz]

Rodney's method in Photoshop:

Here's how to do it In photoshop

1) Convert to 8 bit greyscale

2) Resize the image to the size its gonna get engraved using 150-300 dpi (150 for less detail)
(You can do the same thing in Corel Photopaint)

3) Bump up contrast and brightness about +25 in
both cases - you dont want the pic to be insipid areas of medium grey.

4) Heres the VITAL part - use unsharp mask at 500% and a radius of 3-5 pixels - threshold 0 - this will exaggerate edges radically , but thats what you need. In fact you can do this and then STILL add another unsharp mask at 150 % , 1pixel and 0 threshold AFTER the 1st unsharp if you want even more edge detection

5) Convert to a bitmap using 125-150ppi and a diffusion pattern.

5) laser.

Here's the macro itself, coded up by Doug:
http://www.dogcollarlabor.com/smc/index.html

[Joe Hillmann]

Thanks Dan

[Dan Hintz]

And one of Frank's threads describing it with an executable:
http://www.sawmillcreek.org/showthread.php?91076-Converting-programs-for-Engraving-Manual-Method-and-Adobe-Photoshop

[Scott Shepherd]

Rodney's method in Photoshop:


Here's the macro itself, coded up by Chuck:
http://www.dogcollarlabor.com/smc/index.html


Coded up by Doug, wasn't it?

[Doug Griffith]

It was Doug. The macro is sitting in a remote corner of my server.

[Joe Hillmann]

There doesn't happen to be a macro for CorelDraw is there?

[Doug Griffith]

If there is one, let me know and I'll put on the server.

[Dan Hintz]

Coded up by Doug, wasn't it?

Fixed.....

[Scott Shepherd]

Yeah,don't make Doug mad, he'll create something that recognizes you personally every time you walk out the house and it'll turn the sprinkler on and hose you down every day :)

[Joe Hillmann]

What about just a step by step in CorelDraw? I have no problem until I get to step 4 in Dans response. I don't know if Corel has a unsharpen mask or the ability to set it to a radius of 3-5 pixels.

[Joe Hillmann]

I managed to figure out step four(I don't do much work with bitmaps so didn't know what options there were).

Do you laser the 8bit gray scale image or do I convert it to 1 bit black and white once I have gone through the steps?

[Dan Hintz]

Do you laser the 8bit gray scale image or do I convert it to 1 bit black and white once I have gone through the steps?

I always printed the grayscale... ULS does a fine job converting to 1-bit. YMMV...

[Robert Silvers]

I managed to figure out step four(I don't do much work with bitmaps so didn't know what options there were).

Do you laser the 8bit gray scale image or do I convert it to 1 bit black and white once I have gone through the steps?

Diffusion dither as used in the Gold method needs a brighter image than conversions that use line screens. The Gold method knows this, and lightens the image. If your printer uses the same diffusion dither then you can skip the last step, but if your printer uses a line screen, then you can't skip the last step and have it be the Gold method.

[Rodne Gold]

I put in the last step to bypass any driver software and to ensure consistency , at the end of it all , you send a 1 bit file to the laser , which is smaller than greyscale and it cant mess up with its own processing that can lead to banding etc...

In terms of photo engraving , there is a lot more to it than just dithering , the laser cannot really hold a resolution better than 50-100ppi , it can do more dpi - up to a max of 300 dpi as 0.003" is the smallest spot size you can get for the lasers , but ppi and dpi are not the same thing , to represent a shade of grey , the "dots" (spots or dots per inch) has to be in a matrix (pixel with a shade of grey)
000
0X0
000
would be a pixel with the lightest shade of grey where X is the dot
and
XXX
XXX
XXX
Would be a black pixel , so you can see a dot does NOT represent a shade of grey , it has to be in some matrix...so dots per inch does not really map to the resolution.

Your spot size is of importance , the matrix will be bigger overall if your spot is big , otherwise it "overwhelms" the smaller matrix and you lose resolution

Then of course , it's also dependent on what resolution the material can hold , anodised ally or granite can hold far finer resolution than wood , as there is huge dot gain on wood and on certian other mateirials
Of course the contrast of the mark on the lasered material and often grain of the material come into play
And then the other factor is that a lot of pics you get to be engraved are great in colour , but when you convert to B&W , they are far less suitable for laser engraving
Then there is the factor of time , both in prepping the artwork and in terms of engraving it
Then of course there is customer expectation..they do not want or expect the laser to be totally photorealistic and are pretty happy that their pic is recognisable.
Of course the size of the image is also important , an A2 print is not meant to be viewed at 3" and thus with bigger images , you can get away with a far grosser resolution

i can tell you this , in a big job shop with all my customers knowing I can do pictures , there is little demand for it ..maybe 0.2% of all my work.

[Robert Silvers]

Since some of the machines offer 600 and even 1200 dpi mode, is that just marketing and specsmanship (like claiming crazy contrast ratios on LCD TVs), or does the 1200 dpi mode sometimes produce a better result?

Does it ever make sense to dither to more than 300 DPI? I mean I know it doesn't on my machine, but does it on a US machine?

[Dan Hintz]

0.003" is the smallest spot size you can get for the lasers

Minor correction... 0.001" is generally the smallest, though you need to use a beam expander/collimator setup to get that size (known as HPDFO on the ULS, and I think the Epilogs call it something like Brilliance Optics, but I don't see it listed on their site any more). True 1,000 dpi is certainly possible with this type of setup.

[Dan Hintz]

Does it ever make sense to dither to more than 300 DPI? I mean I know it doesn't on my machine, but does it on a US machine?

Absolutely. Draw 300 dots 3 mils in size along a line. Now draw 600 dots of the same size in the same space. The second will look better.