Scanning Film The Way It Was Meant To Be

March 28, 2025 by Jenny List 37 Comments

Scanning a film negative is as simple as holding it up against a light source and photographing the result. But should you try such a straightforward method with color negatives it’s possible your results may leave a little to be desired. White LEDs have a spectrum which looks white to our eyes, but which doesn’t quite match that of the photographic emulsions.

[JackW01] is here with a negative scanning light that uses instead a trio of red, green, and blue LEDs whose wavelengths have been chosen for that crucial match. With it, it’s possible to make a good quality scan with far less post-processing.

The light itself uses 665 nm for red, 525 nm for green, and 450 nm blue diodes mounted in a grid behind a carefully designed diffuser. The write-up goes into great detail about the spectra in question, showing the shortcomings of the various alternatives.

We can immediately see the value here at Hackaday, because like many a photographer working with analogue and digital media, we’ve grappled with color matching ourselves.

This isn’t the first time we’ve considered film scanning but it may be the first project we’ve seen go into such detail with the light source. We have looked at the resolution of the film though.

Home Depot Lamp Gets A Rainbow Upgrade

February 14, 2025 by Lewin Day 14 Comments

Home Depot has at times sold a neat spiral lamp that relies on LEDs to supply its soothing white glow. When [Craig Lindley] saw some modified versions on YouTube he decided he had to build one himself. The result is a charming rainbow lamp that really lights up a room (pardon the pun).

[Craig] first set about stripping the lamp of its white LED strips, replacing them with addressable WS2812B LEDs. No more would the lamp just output white light—any color in the RGB gamut was now on the table.

A powerful 10 amp 5 volt power supply was then installed to provide the necessary juice. A Wemos D1 Mini was pressed into service as the controller, which was also hooked up to an HC-SR04 infrared motion sensor. This provided the capacity to trigger the lamp when it detects someone moving nearby.

Alternatively, the lamp was given a time-activated mode as well. Either way, when activated, the lamp displays a range of colorful patterns on its elegant spirals, all with the aid of the popular FastLED library.

The final result is impressive—it looks almost stock, except it’s far more colorful and interesting to look at than the original. It’s also amusingly hard to display in our usual image formats because it’s so tall and narrow. In any case, we’ve seen some great lamp builds before, too. If you’re working on your own charming illuminations, don’t hesitate to drop us a line!

Digital Paint Mixing Has Been Greatly Improved With 1930s Math

January 30, 2025 by Lewin Day 41 Comments

You might not have noticed if you’re not a digital artist, but most painting and image apps still get color mixing wrong. As we all learned in kindergarten, blue paint and yellow paint makes green paint. Try doing that in Photoshop, and you’ll get something altogether different—a vague, uninspiring brownish-grey. It’s the same story in just about every graphics package out there.

As it turns out, there’s a good reason the big art apps haven’t tackled this—because it’s really hard! However, a team of researchers at Czech Technical University has finally cracked this long-standing problem. The result of their hard work is Mixbox, a digital model for pigment-based color mixing. Once again, creative application of mathematics has netted aesthetically beautiful results!

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Upgraded Raster Laser Projector Goes RGB

September 18, 2024 by Dave Rowntree 10 Comments

We’ve covered a scanning laser project by Ben Make’s Everything last year, and now he’s back with a significant update. [Ben]’s latest project now offers a higher resolution and RGB lasers. A couple of previous versions of the device used the same concept of a rotating segmented mirror synchronised to a pulsed laser diode to create scanlines. When projected onto a suitable surface, the distorted, pixelated characters looked quite funky, but there was clearly room for improvement.

More scanlines and a faster horizontal pixel rate

The previous device used slightly inclined mirrors to deflect the beam into scanlines, with one mirror per scanline limiting the vertical resolution. To improve resolution, the mirrors were replaced with identically aligned mirrors of the type used in laser printers for horizontal scanning. An off-the-shelf laser galvo was used for vertical scanning, allowing faster scanning due to its small deflection angle. This setup is quicker than then usual vector galvo application, as the smaller movements require less time to complete. Once the resolution improvement was in hand, the controller upgrade to a Teensy 4 gave more processing bandwidth than the previous Arduino and a consequent massive improvement in image clarity.

Finally, monochrome displays don’t look anywhere near as good as an RGB setup. [Ben] utilised a dedicated RGB laser setup since he had trouble sourcing the appropriate dichroic mirrors to match available lasers. This used four lasers (with two red ones) and the correct dichroic mirrors to combine each laser source into a single beam path, which was then sent to the galvo. [Ben] tried to find a DAC solution fast enough to drive the lasers for a proper colour-mixing input but ended up shelving that idea for now and sticking with direct on-off control. This resulted in a palette of just seven colours, but that’s still a lot better than monochrome.

The project’s execution is excellent, and care was taken to make it operate outdoors with a battery. Even with appropriate safety measures, you don’t really want to play with high-intensity lasers around the house!

Here’s the previous version we covered, a neat DIY laser galvo using steppers, and a much older but very cool RGB vector projector.

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A very tiny keyboard with RGB backlighting.

Tiny Custom Keyboard Gets RGB

August 23, 2024 by Lewin Day 9 Comments

Full-size keyboards are great for actually typing on and using for day-to-day interfacing duties. They’re less good for impressing the Internet. If you really want to show off, you gotta go really big — or really small. [juskim] went the latter route, and added RGB to boot!

This was [juskim]’s attempt to produce the world’s smallest keyboard. We can’t guarantee that, but it’s certainly very small. You could readily clasp it within a closed fist. It uses a cut down 60% key layout, but it’s still well-featured, including numbers, letters, function keys, and even +,-, and =. The build uses tiny tactile switches that are SMD mounted on a custom PCB. An ATmega32U4 is used as the microcontroller running the show, which speaks USB to act as a standard human interface device (HID). The keycaps and case are tiny 3D printed items, with six RGB LEDs installed inside for the proper gamer aesthetic. The total keyboard measures 66 mm x 21 mm.

Don’t expect to type fast on this thing. [juskim] only managed 14 words per minute. If you want to be productive, consider a more traditional design.

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The BAPPR Keeps Your Addressable LED System Cool

July 27, 2024 by Alexander Rowsell 17 Comments

We all love a nice strip or grid of addressable LEDs. It can add flair or an artistic touch to many projects, and it can make gaming computers look extra 1337. However, providing enough current to a long strip of addressable LEDs can sometimes be difficult. Often a separate voltage rail is needed to supply enough juice. At the same time, continually sending out data to animate them can often use 100% of the microcontroller’s CPU power, especially if the serial bus is being bit-banged. A crash or badly timed interrupt can leave the system in a weird state and sometimes with the LEDs not displaying the correct colours. Or you might just want to enter a power-saving mode from time to time on your main MCU? Well, the BAPPR is designed to address all of these problems.

[TheMariday] created the BAPPR and made it fully open-source. It’s a switch-mode power supply that can accept anywhere from 7 V to 17 V and converts it into a strong 5 V rail for typical addressable LEDs. It also has a “smart” mode where it monitors the data line going to the LEDs to see if there is activity. If for some reason the system stops sending data, the BAPPR can intervene and shut off the power to the LEDs, which can help prevent strange colour combinations from being displayed while the system recovers. Once data starts flowing again, power is restored and the light party can resume.

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How To Cram 945 LEDs Into A Teeny Tiny Vegas-Style Sphere

May 31, 2024 by Donald Papp 18 Comments

[Carl Bugeja] finds the engineering behind the Las Vegas Sphere fascinating, and made a video all about the experience of designing and building a micro-sized desktop version. [Carl]’s version is about the size of a baseball and crams nearly a thousand RGB pixels across the surface.

A four-layer flexible PCB is the key to routing data and power to so many LEDs.

Putting that many addressable LEDs — even tiny 1 mm x 1 mm ones — across a rounded surface isn’t exactly trivial. [Carl]’s favored approach ended up relying on a flexible four-layer PCB and using clever design and math to lay out an unusual panel shape which covers a small 3D printed geodesic dome.

Much easier said that done, by the way. All kinds of things can and do go wrong, from an un-fixable short in the first version to adhesive and durability issues in later prototypes. In the end, however, it’s a success. Powered over USB-C, his mini “sphere” can display a variety of patterns and reactive emojis.

As elegant and impressive as the engineering is in this dense little display, [Carl] has some mixed feelings about the results. 945 individual pixels on such a small object is a lot, but it also ends up being fairly low-resolution in the end. It isn’t very good at displaying sharp lines or borders, so any familiar shapes (like circles or eyes) come out kind of ragged. It’s also expensive. The tiny LEDs may be only about 5 cents each, but when one needs nearly a thousand of them for one prototype that adds up quickly. The whole bill of materials comes out to roughly $250 USD after adding up the components, PCB, controller, and mechanical parts. It’s certainly a wildly different build than its distant cousin, the RGB cube.

Still, it’s an awfully slick little build. [Carl] doubts there’s much value in pursuing the idea further, but there are plenty of great images and clips from the build. Check out the video, embedded below.

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