Continuing from For you Civil War buffs,
First of all, I applied the gradient map technique to the image to increase the contrast. Then, knowing I would likely not be able to get this image through the GFUI in one go due to its size and complexity, I needed to divide it up. But I didn’t want to risk visible lines in the output, so I used a modified version of @Jules’ no-lines method for splitting up an image.
In her demo, she was using a vector image that had a lot of contiguous dark areas. My image didn’t have that, so I changed the process a little.
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After cleaning up the image and converting to grayscale, I posterized it to 6 levels (three grays, black, white, and transparent).
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I zoomed way in to enlarge the pixels, selected and deleted white pixel non-contiguously. So we were down to three grays and black.
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Selected the darkest (black) non-contiguously, copied it to a new layer, and deleted the black from the original layer.
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Repeated this on two more grays. The remaining layer had the palest grays (strangely, more than one). I think at some point I changed the mode back to RGB so I could export as PNG.
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Exported each layer as PNG. Reassembled all layers in Illustrator (aligned to each other), and added a cropping rectangle. Saved as SVG.
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In the GFUI, I had four operations with varying levels of gray, plus a cut line.
I did an engrave test on Baltic birch using Photo engrave defaults (speed 600, power 58, convert to dots) except that I used a range of 0-65 instead of 0-100, and I used 270 LPI instead of 450. My test came out okay except all those paler grays really muddied up the image. So for the one on maple ply I set the engrave order to start with the darkest grays first, then progress to the lightest, one at a time. Each level took one hour. After two gray levels had engraved, I decided to stop engraving and do the cut, to avoid the muddying of the background that the lighter grays seem to cause. That did cause the clouds in the image to pretty much drop out but I couldn’t keep them as well as the detail in the lower part of the image.
