Scale/Scape: Halftone Light Panel Series

Scale/Scape is a series of light panel images developed in a three month artist residency at Pier 9 in San Francisco. The project is an investigation into the thresholds of human perception and the history of halftone printing techniques. Images from microscopic and telescopic scales are transformed into light patterns formed by thousands of dots of different sizes. Custom software translates pixel clusters into laser-cut holes of different sizes, and strangely when the image is more blurred, it becomes more recognizable. Some pieces are blurred from distance and the weakness of human vision; and some are optically blurred with raised translucent diffusion panels.

I made nine pieces in this series while at Pier 9, plus another four pieces that I didn't like enough to show. The nice pieces included three window mounted light panels, three small illuminated light boxes, two large illuminated light boxes, and one experimental light box with a motorized blur panel.

This documentation follows through the course of building these pieces but with a lot of repetitive material omitted for brevity. This Instructable is documentation for the entire series as an art project.

Step 1: Early Version 1: Abstract Lines

The project is a continuation of a much earlier piece I did in 2005 before I had access to digital fabrication tools. At the time I was deeply immersed in physically interactive art work, making a lot of custom circuitry and software, and I wanted to take a break to make a simple object with my hands. I became interested in graphic light alternatives to LEDs, something that looked more sophisticated than it was. I started with a opaque MDF an opaque front surface, drew an abstract pattern of flowing lines, and drilled holes into it to let light through. I made a simple lightbox out of MDF and covered the penetrated surface with a diffusing layer of translucent plexi. Circular fluorescent bulbs inside the box made some holes brighter than others, which provided a nice organic quality. This piece was just a quick experiment, a departure from the over-complex headaches of my other work. But I liked how it turned out, specifically how the points of light made your eye continue the line, how our brains are hardwired to fill in missing information.

Step 2: Early Version 2: Ant

In 2005, I made a second piece in the series with a more complex image and technique. Starting with a microscopy photograph of an ant's head, I used an image editor to transform the image into clusters of dots. This led me to research into halftoning, the old printing technique to simulate greyscale using only black ink. I'll get into this in more detail in future steps. For this early piece, I only had a drill press to make the holes, this was 2005 before I had a laser cutter. So I drilled holes closer together where the image was darker, and farther apart where it was lighter. In halftone parlance, this was FM (Frequency Modulation), rather than AM (Amplitude Modulation). Yes the same terms as radio :-). About 1,000 holes, drill, drill, drill. Drill.

Again, I covered the drilled panel with a translucent layer of plexi. When the box was off, it looked like a grey rectangle. When turned on, the image appears, and different areas seem to have shading and gradations even beyond the dot spacing, due to the bulb shapes hidden inside. I liked that from far away, it seemed to be a sophisticated LED illustration, but it was actually just light bulbs and holes.

The finished piece was attractive but a bit clumsy from all the hand-drilling and inaccurate brightness-to-dot-spacing. But I liked it, and that was that, until 9 years later...

Step 3: Halftones and the Advantage of Weakness

Halftone printing was invented in the 1830s. In brief, it simulates continuous tones with only one color through the use of dots of different size or different spacing. It is still used in newspapers and other printed material today. I was interested in the history of this technology, how it depended on an optical illusion and in fact on the weakness of the human visual system. When our eye is farther from a surface, its details start to blur. This limitation is taken advantage of by halftone patterns, as the dots blur together and seem to be shades of grey rather than individual points. Our brain then does what it does best, which is fill in missing information, recognize patterns, and assign depth and meaning.

In a normal halftone print, the smallest dots and tightest density is ideal, since the image maker only wants the viewer to see the image, not its constituent parts. What happens when we make an image right on the edge between recognizable and abstract, that is both about its meaning and its building blocks? Taking a technique devised as a workaround and highlighting the oddness and ingenuity of its mechanism. In the case of cutting holes, rather than printing dots, the image was inversed, using light to stand in for dark, and solid material to stand in for empty paper.

With all of this in mind, and with my new access to high-end laser cutters, I started work on a new series of images. In addition to foregrounding the halftone process, I looked for images from scales normally not visible to the human eye. Microscopic and telescopic photographs, from the very tiny to the incredibly large and distant.

Step 4: Halftone Software Development

In order to transform an image into a halftone pattern, I needed to write some custom software. The algorithms aren't terribly complicated, but I wanted to be able to control the minimum and maximum size of the dots AND the spacing between them. I used Processing to write the software, my favorite free coding development for simple tasks. (I use OpenFrameworks for heavier duty stuff.) The basic idea is:

Scan through the pixels of an image and find their average brightness value in blocks of the same size as dot spacing.
Minimum diameter = just above black; maximum diameter = white
Draw a filled circle in the center of each block with a diameter mapped to brightness
Output a vector file that can be read by laser cutters

I chose to show the halftone pattern on screen as white dots on a black background, the reverse of a normal halftone print which usually has black ink dots on empty white paper. In this case, since the dots would be cut out and light would shine through, an inversed preview made more sense - the white dots represent light and the black background represents whatever solid material the dots are being cut out of.

The file output, however, must be a standard black on white to be read by laser cutter print drivers. Critically, the dots must be rendered as empty circles and not filled. This way the laser cutter cuts out the circle rather than etches a filled pattern.

After experimenting a bit, I added some more features:

Image overlay opacity control bar
Image Black and White Threshold controls
Dot Stagger toggle button to get a slightly denser pattern

It's nice to compare the source image with the halftone pattern, and sometimes an overlay works better. I also added a keyboard shortcut ("i) for quick toggling.

The threshold control helps if an image has a dark but not black background, and I want empty space instead of a tiny dot fill throughout the background. It also helps if the brightest parts of the image are not white, so the dot diameter mapping extends over the entire range.

The dot stagger pattern looks a bit more natural from far away and allows for bigger dots with the same spacing because of diagonal gaps instead of just vertical and horizontal. This is especially important once I start to laser cut, because the material is in danger of falling apart in very thin areas between dots.

Step 5: Halftone Software Use

The first image I chose was from a series of microscope photographs of bees, collected in the USGS Bee Inventory and Monitoring Lab. All of these images are public domain, being paid for by tax payers. I experimented with over a dozen images, and chose one that had a strong side profile with high contrast, an empty black background, and recognizable banding on the bee body.

I experimented with dot size and spacing quite a bit. I wanted the image to be recognizable, but near-abstract when very close. The viewer's eye should oscillate between the pattern of dots and the relationship between the dots, the illusion of depth and shading.

The tighter the dot spacing, the more obvious the image is. But I didn't want to make the image look as clear as possible. Again, in direct contradiction to the history and purpose of halftoning, which usually tries to represent the image as thoroughly as possible. The re-use and subversion of this technique interested me. I was taking an incredibly high resolution photograph and deliberately making it incredibly low resolution.

Another factor was the time needed to laser cut. The dot spacings I liked resulted in files with 4,000 - 10,000 dots. More than 8,000 dots got too crazy on the laser cutter, which I will describe in the next step. So I tried to keep the spacing wide enough that the dot total was under 8,000, without the image getting too hard to recognize.

I also added a few new features to the software:

An actual size estimate in inches for dots, based on overall material size
A Dot Count display, so I would know approximately how long it would take to laser cut
PDF line thickness of 0.7pt (<0.01"), which ensures laser cutter reads lines as Cut, not Etch
File export with the settings written into the filename, so I could keep track of iterations and recreate settings easily
A two-part export, one with a white background for the lasercutter, one with a black background for quick previews later and easy comparison of different settings

If the minimum dot size is smaller in diameter than the thickness of the material, you only see the light shining through it when you are directly in front of it. The thinner the material, the more of the dots and thus the more of the image you can see from the size. However, thicker material was more structural, i.e. not prone to sagging, especially for the bigger light boxes I knew I was going to make. After entering my material width and height into the software, the dot size display would tell me how the smallest diameter compared to my thickness. I could also adjust the size in inches, rather than in pixels, by dragging that control bar.

The file export name feature resulted in filenames like "bee-side dots4865 min02.02 max07.04 spc12 blk17_wht255" (dimensions in pixels), which made it easy to keep track of what quickly became folder after folder of experimenting.

Step 6: Laser Cutting Dots

Once my software outputted halftone dot files I liked, I thought, super, that's the hard part. Boy was I wrong. Laser cutting the dots proved to require many, many hours of trial and error. And once perfect settings were found for a given file with a given spacing with a given material with a given thickness, even changing to a different laser cutter with the same wattage would produce slightly different results.

The biggest issue was finding settings that ensured the dots were fully cut out and not stuck in the material. As with all laser cutting, the primary balance is between speed and power. Too slow or too powerful and the material would burn or warp. Too fast or too weak and the holes would not be fully cut out, requiring hours of poking out with a needle.

For each image, I took a small sample with the biggest possible range of dot sizes. Then I made a matrix adjusting speed on one axis and power on the other. With most materials I could not tell what percentage of dots were fully cut out until the sheet was out of the laser cutter and shook out and/or blown with the air compressor. The optimal settings were highly specific - 1 point difference out of 100 was significant. Eventually I settled on a result that still required some clean up after the fact, but without too much material distortion. A combination of shaking, blue tape application and peeling, and manual poking with a thin tool was necessary for each piece.

I also found that spacing the material off of the laser cutter grid substrate improved the finish, reducing the burn-back effect. I used scraps of ply or acrylic for this, making sure to tape down my material to keep it absolutely flat so the laser focus would stay consistent.

Step 7: "Bee" Light Panel Series # 1

To create my first Light Panel box, I chose a nice cherry hardwood. It had a nice reddish tone with a visible but not overly distracting grain. I cut a 12" x 9" piece and reduced the thickness in the planer to about 1/8". I tried a few different thicknesses, and found that 1/8" was the absolute thinnest I could get away with. At first I thought I would need my minimum dot diameter to be 1/8", so that the light shining through those dots could be seen from the side. However with that setting, I needed a very large maximum dot size, which then constrained the spacing setting I needed so that dots didn't overlap (which would result in the material falling apart) - and if I also widened the spacing, the image was so low resolution it wasn't recognizable any more.

As is often the case, a problem sparked an idea. With the tests I did with a minimum dot size smaller than 1/8", as I moved my head laterally to the side of the material, the smaller dots would progressively disappear. Ostensibly a bad thing - but I found it looked interesting, if I chose the minimum and maximum sizes carefully so that the effect was balanced. It produced an occlusion effect that had a sort of moiré feel, and emphasized the contrast between light and dark areas, as well as producing a "reveal" effect as a viewer moved from extreme angles to the front of the image.

For this image I used the following settings with an Epilog Legend 36EXT 120 watt laser -

1/8" hardwood (cherry) with 0.02" actual minimum dot size: Speed 21, Power 65, Frequency 500

Step 8: Box Frame Construction

I created a series of light boxes for each lasered halftone panel. The basic idea was to backlight the perforated panel, with the minimum distance needed to house the lights and have diffusion to even out hot spots. I tried both fluorescent and LED lighting. Both are relatively cool and energy efficient, with fluorescent being slightly cheaper but heavier, and LEDs having more color tone choices.

The box sides were either hardwood or ply, 1/2"-3/4" thick, mitered to 45° angles for nice corner joints. The back side was 1/8" or 3/16" ply.

The miter joints were cut with a sled on a table saw set to 45° with protractor verification. Using a chop saw was simply not accurate enough.

I first built clamp jigs to provide consistent pressure across the mitered joints. These were flat scrap boards cut to slightly less than the lengths of the frame pieces, with 45° scrap blocks glued and screwed in. Later, I discovered a good strap clamp made these unnecessary.

Step 9: Box Joints and Back Panel

Some boxes also had spline joints to strengthen the corners and provide a handsome accent. The splines were 1/8" thick pieces of a darker wood, rough cut and inserted into grooves cut into the joints with the table saw. I made a spline joint jig to hold the frame corners at a 45° angle as it runs through the saw. The spline joint jig was made from two pieces of 3/4" ply screwed together, with a perfect 90° notch cut into it. I cut the spline pieces with a Thin Rip Tablesaw Jig, although you can just use the normal fence if you don't mind kickback. I glued the splines into the grooves, rough cut the excess with the bandsaw, and then sanded down with the orbital sander.

Before attaching the back panel, I routed out a small groove for the electrical cord to fit through. With the cord in place, I screwed the back panel on, which was easy, but it was visible from the side. On the next boxes I made a rabbet cut with the table router, and then inset the back panel flush into the frame.

Step 10: Lighting and Electrical

I used Warm White LED strips stuck to the back panel with double-sided tape. On the small boxes, a few rows were bright enough. On the big boxes I used double row, high density strips. The LED strips used a 12V power supply. In the first box, I fit the power supply inside, so only a standard AC plug was showing on the outside.

I put the LEDs in the box asymmetrically because of the composition of the Bee image. In order to make the illumination as even as possible, I the inserted a layer of diffusion material. I tried many different kinds, including industry standard "Sign White", 1/8" translucent white with 40% light pass through. A rigid material was easiest to assemble, but I ended up preferring a very thin flexible textured material often called "LED Diffusion Film."

Even though the pattern of LEDs was still slightly discernible after diffusion, it didn't matter once the top laser cut layer was put on top.

Step 11: Box Assembly

I used threaded inserts to attach the panels, and in some cases to attach an additional blurring layer of translucent acrylic, to be detailed in the next step. The inserts were installed with a drill on low speed, medium torque using a bolt and nuts of the same threading, with a bit of glue to lubricate and strengthen. Normally you would never put an insert in a mitered corner, but I thought I would give it a try because I wanted the hardware to be in the far corners, so they wouldn't distract from the image. I had to drill pilot holes much bigger than the recommended size for the inserts, and use more glue around the insert to make sure the joint strength wasn't compromised. It wasn't the best idea, in later iterations I moved the insertion points in from the corners and it looked fine.,

I drilled holes in the corner of the front panel for attachment hardware to pass through. Then I screwed in hex bit low profile pan head bolts with a washer into the threaded inserts.

Step 12: "Bee, Caupolicana Gaullei" Light Panel Series #1

Bee, Caupolicana gaullei (2015)

Scale/Scape Light Panel series #1

9" x 12" x 2"

Cherry hardwood, plywood, LED illumination, acrylic diffusion film, metal hardware

Step 13: "Water" Light Panel Box Construction

This image was taken from a photograph of water surface. It was near abstract to begin with, so the halftone version was in danger of being unrecognizable. In order to help the viewer see the "missing" information, I added a blur panel spaced above the front panel. The blur panel was clear plexi that I sanded on one side with an orbital sander, starting at 120 grit down to 800. It was very difficult to get an even finish and I eventually switched to Acrylite P95 with a matte finish.

This time I made the LED strips a little more orderly. I drilled the mounting holes through the diffusion acrylic, wood panel, and blur acrylic layer simultaneously. I used aluminum spacers with carefully chosen height to offset the blur panel. I used longer versions of the hex head bolts to attach the panel, passing through all three layers and the spacer into the the threaded insert.

I sealed the wood with a satin clear finish.

Step 14: "Water", Light Panel Series - Rejected

Water (2015)

Scale/Scape Light Panel series - eliminated

9" x 16" x 3"

Plywood, acrylic, metal hardware

I wasn't thrilled with this one, so I set it aside. I sealed the wood with a clearcoat, and the end color was too light, which affected the contrast with the illuminated dots. It was just too abstract, no matter how much I blurred the image.

Step 15: "Human Hair" Light Panel Series #2

Human Hair (2015)

Scale/Scape Light Panel series #2

9" x 16" x 3"

Stained hardwood, fluorescent bulbs, plywood, black, diffusion, and blur acrylic, metal hardware

(source credit: Stefan Diller, scanning electron microscope)

This piece I used black acrylic for the surface material, which provided really strong contrast with the illuminated dots. The lighting was fluorescent for this one, which gave very even light diffusion, although the piece was much heavier. The blur layer was again hand-sanded clear plexi, which looked pretty good straight on, but dimmed the image a bit too much when viewed from the side. I sanded the black acrylic for a nice matte finish, and added a set of flat head black machine bolts in the middle to keep the layers tight, counter-sunk into the black acrylic. I also added an old-fashioned toggle switch with a wood accent.

I ended up displaying this one without the blur panel.

Step 16: "Gullies, Mars" Light Panel Series #3

Gullies, Mars (2015)

Scale/Scape Light Panel series #3

9" x 16" x 2"

Stained wood, LED illumination, acrylic, metal hardware

(Source credit: NASA/JPL)

In this piece, I used an aerial photograph of a Martian landscape which could as easily be a mountain range on Earth. I stained the front wood panel a dark walnut color to bring out the contrast. The first iteration had a blur panel spaced 1/2" off the wood panel. It looked pretty good, and I liked that the viewer could peer behind the blur panel to see the lasercut dot pattern. This oscillation in the viewer between the near-abstract dot pattern and the blurred recognizable image was really what I was after. In this iteration, the blur panel was so close it was difficult to see underneath it. Increasing the size of the aluminum spacers improved this, but made the image too blurry.

I had a minor breakthrough when I tried cutting down the blur panel to expose some of the dots completely. Now the difference between unblurred and blurred dots was really dramatic. I left the panel a bit longer vertically to give it some compositional balance.

Although I really liked this partial blur effect, I also decided to leave this piece without the blur panel for the exhibition. I did use the partial blur panels for the big pieces, detailed in the next steps. It made more sense when shown as a group to have the large pieces blurred and the small pieces unblurred, since a viewer standing far enough away to see the large pieces would see the small pieces blurrier due to visual acuity falloff.

Step 17: Large Light Panel Series #4-#5: Frame Miter Joints

I made two large pieces with same size and material: 32" x 24" and all hardwood (wenge), with fancier joinery.

I chose a very dark wenge hardwood for these pieces. I planed the pieces to exactly 3/4" thick and cut down into 2" wide planks. Then I cut two 32" and two 24" pieces for each piece.

To make an attractive and structurally superior miter joint, I used a Lock Miter router bit. This bit is awesome but requires a LOT of set up time. It has to be absolutely precise in height and in fence depth, and your work has to be pass through it at precisely 90°. I might publish a separate Instructable on my trials and error and eventual technique for setting up this bit.

The first step was to build a jig to ensure my frame pieces were at exactly 90° to the router fence. I lasercut three L shapes out of 1/4" ply because it was all I had lying around and glued them together. Then I clamped by frame pieces with a lead piece of scrap to run clean through the bit.

Then I aligned the bit carefully using a combination of measurements, a height alignment jig, and trial and error with scrap of the same thickness. First I cut off a bit of the edges with the chip saw at 45° to reduce the load on the router bit. Then I made one pass on the router perpendicular to the fence for the left and right pieces, and one pass perpendicular to the table for the top and bottom pieces. This is to make the profiles inversed and "lock" together.

Step 18: Large Series: Frame Dadoes

I cut two dadoes into my frame pieces with the table saw. One groove is for the back panel, and one wider groove for the front panel plus diffusion layer. I made the wider groove with multiple passes on the table saw.

Step 19: Large Series: Lighting

I had to do the lighting and layering before I glued up the frame because, unlike my earlier pieces, this one could not be opened up once glued.

I set up the frame but did not glue anything, just loosely held together by the friction of the lock miter joint. I cut a back panel of 1/8" ply and slid it into the frame dadoes. This would hold the LED strips.

I used a double-row LED strip for brighter illumination. Warm white again. Double-stick tape plus some clear brackets to ensure nothing peeled off. Rather than cut into pieces and wire lots of connections, I just bent the strip around for each row.

I drilled a small hole in the center of the bottom frame piece for the LED power wire to go through. I had to remember to thread this through first before connecting anything!

Step 20: Large Series: Lasercutting

After days of experimentation with different images and halftone settings in my software, I decided on two and exported to the laser cutter. There were about 7,500 holes per image, so I had to split the file up into four pieces so export from Illustrator or Corel Draw wouldn't crash the laser cutter.

Lots of little dots were left behind in the laser cutter, but I still had to poke out lots more in the panel.

Then I sanded the panel on a dust extraction table, from 120 grit down to 400. This removed any vestigial burn marks from the laser.

Step 21: Large Series: Wood Staining

I tried out numerous stains and finishes. I settled on Moorish Teak, which was almost as dark as Walnut but had a bit of red in it. It didn't match the wenge exactly but it was close enough.

After staining the panel, I blew out the holes with the air compressor to make sure no stain was clogging them. Then I wiped those areas down on the reverse side.

After I left the stain soak in for a few minutes, I rubbed the whole panel down fairly aggressively to bring out the grain contrast. With no back lighting, it is almost impossible to tell what the image is, which is what I wanted.

Step 22: Large Series: Frame and Panel Assembly

This was tricky. Because the panels were thin, they sagged a bit even after slid into a dado groove. And all four frame pieces had to be fit together simultaneously, with glue, so the panels had to fit cleanly into the groove at the far edge of the open side where I was sliding them in.

I did several dry runs and then glued up and went for it. Once I had it all together I used a strap clamp with corner fittings to cinch everything tight. There were still slight gaps and misalignment on the corners so I added some bar clamps to tweak the fit.

Step 23: Large Series: Blur Panel Assembly

I lasercut P95 acrylic for the blur panels, including mounting holes in four corners. I aligned those holes on the frame and marked with a center punch. Then I put the whole assembly on the drill press and made pilot holes for threaded inserts. I used #10 inserts and drilled pilot holes a bit deeper than the inserts, to make sure there was enough meat on the bolts that the weight of the large panel would not bend the mounting spacers.

I put the inserts in with a drill on low speed with low torque, using a bolt with nuts as the insertion tool.

I tested various spacing between the image panel and the blur panel and settled on 3/4" spacers, which when added to the frame inset, was 1 1/4" total spacing. I attached the blur panel with low profile hex head bolts.

Finally I added some picture hanging wire to the back of the frame.

Step 24: "Victoria Crater, Mars" Light Panel Series #4

Victoria Crater, Mars (2015)

Scale/Scape Light Panel series #4

24" x 32" x 3"

Wenge hardwood, stained plywood, LED illumination, acrylic, metal hardware

(Source credit: NASA/JPL)

Step 25: Victoria Crater, Mars - Natural Light Version

Victoria Crater, Mars [Natural Light] (2015)

Scale/Scape Natural Light series #4B

22" x 24" x 1/8"

Lasercut Matte board

(Source credit: NASA/JPL)

I also made a series of images lasercut into black matte board that can be hung in a window and take advantage of natural light. This was a nice low-budget version that uses zero electricity. The downside of course is that the image is not visible at night. Hanging the piece in a window allows the background to show through the image, creating an interesting layered effect.