The F Number On A Lens Means Something? Who Knew!

March 18, 2024 by Jenny List 58 Comments

The Raspberry Pi has provided experimenters with many channels of enquiry, and for me perhaps the furthest into uncharted waters it has led me has come through its camera interface. At a superficial level I can plug in one of the ready-made modules with a built-in tiny lens, but as I experiment with the naked sensors of the HD module and a deconstructed Chinese miniature sensor it’s taken me further into camera design than I’d expected.

I’m using them with extra lenses to make full-frame captures of vintage film cameras, in the first instance 8 mm movie cameras but as I experiment more, even 35 mm still cameras. As I’m now channeling the light-gathering ability of a relatively huge area of 1970s glass into a tiny sensor designed for a miniature lens, I’m discovering that maybe too much light is not a good thing. At this point instead of winging it I found it was maybe a good idea to learn a bit about lenses, and that’s how I started to understand what those F-numbers mean.

More Than The Ring You Twiddle To Get The Exposure Right

lose-up of the end of a lens, showing the F-number range — The F-number range of a 1990s Sigma consumer-grade zoom lens.

I’m not a photographer, instead I’m an engineer who likes tinkering with cameras and who takes photographs as part of her work but using the camera as a tool. Thus the f-stop ring has always been for me simply the thing you twiddle when you want to bring the exposure into range, and which has an effect on depth of field.

The numbers were always just numbers, until suddenly I had to understand them for my projects to work. So the first number I had to learn about was the F-number of the lens itself. It’s usually printed on the front next to the focal length and expressed as a ratio of the diameter of the light entrance to the lens focal length. Looking around my bench I see numbers ranging from 1:1 for a Canon 8mm camera to 1:2.8 for a 1950s Braun Paxette 35 mm camera, but it seems that around 1:1.2 is where most 8 mm cameras sit and 1:2 is around where I’m seeing 35 mm kit lenses. The F-stop ring controls an adjustable aperture, and the numbers correspond to that ratio. So that 1:2 kit lens is only 1:2 at the F2 setting, and becomes 1:16 at the F16 setting.

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Shôtarô Kaneda’s Motorcycle, For Real

March 17, 2024 by Jenny List 25 Comments

For fans of the iconic anime Akira, there’s only one way to traverse the mean streets of post-apocalyptic neo-Tokyo, and that’s the futuristic mount of motorcycle gang leader Shôtarô Kaneda. It’s a low-down feet-forward machine with, we’re told, “Ceramic double-rotor two-wheel drive,” which we’re guessing is some kind of hybrid electric drive with what sounds like a gas-turbine motor. Over the years, there have been a few different attempts to create a real version of Kaneda’s bike, and we’re pleased to see the latest from ヲタ工房「ポンちゃンネル」(Ota Kobo “Ponchanner”). It uses a twin-cylinder Kawasaki motor in an entirely custom-made frame, with dual single-sided swingarms front and rear and hub-centre steering.

The full build in the video below the break is pretty long but well worth a watch, and it includes a lot of very highly skilled metalwork. It’s an interesting choice not to attempt to make a direct replica of Kaneda’s bike. Still, we think some of the differences are dictated by this being very much a roadworthy and everyday-rideable machine.

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The Most Famous Room In Rock-n-Roll You’ve Never Seen

March 17, 2024 by Jenny List 6 Comments

The study of audio technology has a lot of fascinating branches, and one or two of them even take the curious engineer not into electronics but into architecture. There’s the anechoic chamber with its complete lack of echo, but at the other end of the scale, there’s the echo chamber.

It’s normal in 2024 when searching for reverb to reach for a software plugin, but following the effect back through silicon, spring lines, and metal plates to the 1950s, we find an echo chamber as a real room with a speaker and a microphone placed in it. [Rick Beato] takes us into the echo chamber, starting with one of the few remaining originals and probably the one whose effect has been heard on the most highly-charting music, at the famous Abbey Road studio in London.

The video below the break is broadly in two parts, with the first concentrating on the Abbey Road chamber and the second showing how an empty room in a house can be used to make your own. It’s aimed at musicians rather than hardware hackers but we think it’s one of those moments of crossover that readers might find interesting. We were particularly curious about the tall ceramic tubes in the Abbey Road chamber, designed to further break up the sound waves for a greater depth of reverb.

The video shows how reverb can be achieved with just a room, but don’t worry if you’re space limited. A plate reverb needn’t break the bank. Or, grab a spring.

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Glow Plug Turned Metal-Capable 3D Printer Hotend

March 15, 2024 by Jenny List 37 Comments

At this point, most readers will be familiar with fused deposition modeling (FDM) 3D printers, and how a plastic filament is pushed through a heater and deposited as liquid through a nozzle. Most of us also know that there are a huge variety of materials that can be FDM printed, but there’s one which perhaps evades us: you can’t load a spool of metal wire into your printer and print in metal, or at least you can’t yet. It’s something [Rotoforge] is working on, with a project to make a hot end that can melt metal. Their starting point is a ceramic diesel engine glow plug, from which they expect 1300 C (2372 F).

The video below the break deals with the process of converting the glow plug, which mostly means stripping off the metal parts which make it a glow plug, and then delicately EDM drilling a hole through its ceramic tip. The video is well worth a watch for the in-depth examination of how they evolved the means to do this.

Sadly they aren’t at the point of printing metal with this thing, but we think the current progress is impressive enough to have a good chance of working. Definitely one to watch.

Previous metal 3D printers we’ve featured have often used a MIG welder.

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Review: The New Essential Guide To Electronics In Shenzhen

March 13, 2024 by Jenny List 15 Comments

The city of Shenzhen in China holds a special fascination for the electronic hardware community, as the city and special economic zone established by the Chinese government at the start of the 1980s it has become probably one of the most important in the world for electronic manufacturing. If you’re in the business of producing electronic hardware you probably want to do that business there, and if you aren’t, you will certainly own things whose parts were made there. From the lowly hobbyist who buys a kit of parts on AliExpress through the project featured on Hackaday with a Shenzhen-made PCB, to the engineer bringing an electronic product to market, it’s a place which has whether we know it or not become part of our lives.

First, A Bit Of History

A picture of booths in a Shenzhen market — These are the markets we have been looking for. Credit: Naomi Wu.

At a superficial level it’s very easy to do business there, as a quick trawl through our favourite Chinese online retailers will show. But when you’ve graduated from buying stuff online and need to get down to the brass tacks of sourcing parts and arranging manufacture, it becomes impossible to do so without being on the ground. At which point for an American or European without a word of Chinese even sourcing a resistor becomes an impossibly daunting task. To tackle this, back in 2016 the Chinese-American hardware hacker and author Andrew ‘bunnie’ Huang produced a slim wire-bound volume, The Essential Guide to Electronics in Shenzhen. This book contained both a guide to the city’s legendary Huaquanbei electronics marts and a large section of point-to-translate guides for parts, values, and all the other Chinese phrases which a non-Chinese-speaker might need to get their work done in the city. It quickly became an essential tool for sourcing in Shenzhen, and more than one reader no doubt has a well-thumbed copy on their shelves.

There are places in the world where time appears to move very slowly, but this Chinese city is not one of them. A book on Shenzhen written in 2016 is now significantly out of date, and to keep pace with its parts that have since chanced beyond recognition, an update has become necessary. In this endeavour the mantle has passed to the hardware hacker and Shenzhen native Naomi Wu, someone with many years experience in introducing the people, culture, and industries of her city to the world. Her updated volume, The New Essential Guide to Electronics in Shenzhen has been the subject of a recent crowdfunding effort, and I was lucky enough to snag one. It’s a smart hardcover spiral-bound book with a red and gold cover, and it’s time to open it up and take a look. Continue reading “Review: The New Essential Guide To Electronics In Shenzhen” →

This Piano Does Not Exist

March 12, 2024 by Jenny List 9 Comments

A couple of decades ago one of *the* smartphone accessories to have was a Bluetooth keyboard which projected the keymap onto a table surface where letters could be typed in a virtual space. If we’re honest, we remember them as not being very good. But that hasn’t stopped the idea from resurfacing from time to time.

We’re reminded of it by [Mayuresh1611]’s paper piano, in which a virtual piano keyboard is watched over by a webcam to detect the player’s fingers such that the correct note from a range of MP3 files is delivered.

The README is frustratingly light on details other than setup, but a dive into the requirements reveals OpenCV as expected, and TensorFlow. It seems there’s a training step before a would-be virtual virtuoso can tinkle on the non-existent ivories, but the demo shows that there’s something playable in there. We like the idea, and wonder whether it could also be applied to other instruments such as percussion. A table as a drum kit would surely be just as much fun.

This certainly isn’t the first touch piano we’ve featured, but we think it may be the only one using OpenCV. A previous one used more conventional capacitive sensors.

The Insurance Buys The Wheelchair, But Not The App To Run It

March 9, 2024 by Jenny List 34 Comments

The writer Cory Doctorow coined the term enshittification to describe the way that services decline in quality as their users become the product. He was talking about online services when he came up with the word, but the same is very much true when it comes to hardware. Items which once just worked now need apps and online services, with marginal benefit to the user if any. It’s one thing when it’s your soundbar or your washing machine, but thanks to Lemmy user [@win95] from the Netherlands we’ve seen a far more egregious example. People with disabilities are being provided with new powered wheelchairs through their medical insurance, but are then discovering that unaffordable in-app purchases are needed to use their features. Continue reading “The Insurance Buys The Wheelchair, But Not The App To Run It” →