32nd International Meeting of Collectors and Researchers
of Slide Rules and other Historic Computing Instruments

ZOOM meeting on September, 12/13, 2026

Session A            See programme schedule for local times.

• Welcome, organizational issues, survey and start of programme
  Karl Kleine

• Descendants and Relatives to DEMEGRAPH 13
  Jose G. Fernández (ES)
  Jose gave a talk about the Faber-Castell 2/66 and its variants at IM2024, and had an article about it in JOS v33n2. This slide rule was a complex combined rule for many tasks in traditional metal typesetting. Changes in printing technology and standardisation allowed for other solutions, in particular special slide rules for specific tasks and typometers.

• The NORMA Grafia 190 Disk for Graphics Designers and Typographers
  Wolfgang Bode (DE)
  Printers as any other kind of graphic designers always have the problem to fit some text, graphic, logo, whatever to a given medium and size, be it paper, oversized plastic foils, or the pixels of a computer screen. Special circular slide rules were and still are in common use for that, but the NORMA Grafia is simply the best, precise, widely-used, and most beautiful of these.
  [ I (Karl) have found some in a speciality shop for technical drawing and artist's materials in Berlin even in the 200X years — that was just last time I checked ]

• Sound System Slide Rules
  Eamonn Gormley (US)
  Designing a sound system installation for a concert hall, theater, or other venue requires specialized skills, knowledge and calculations. In this presentation we take a look at the evolution of sound system slide chart calculators from the 1940s to the 1990s and the sound system equations that they compute.

Session B            See programme schedule for local times.

• The Watkins Standard exposure meter
  Nathan Zeldes (IL)
  Photography was a complex subject around 1900, with the difficulty of fitting camera bodies, lenses, plates, environmental conditions, in particular the actual light and weather situation, etc together for taking a photo. Alfred Watkins developped and patented in 1890 a little device independent from any camera to measure the actual lighting situation and then to compute from it the necessary exposure time for the photographic equipment at hand.

• Hoh & Hahne Leipzig Special Slide Rule: Solving a Printing Industry Mystery
  Andreas Faßbender (DE)
  This presentation examines a rare special-purpose slide rule manufactured by Albert Nestler for Hoh & Hahne Leipzig, a leading supplier of reproduction cameras for the printing industry. By combining historical research, technical analysis, and original observations, the talk reconstructs the instrument's purpose and demonstrates how it was used to solve lens-distance calculations for image reduction and enlargement in prepress photography. The findings also provide new insights into the rule's manufacture and dating.

• Slide Rules in the Movies
  Karl Kleine (DE)
  Whereas the other presentations of sessions A and B show slide rules for some type of medium for communication, this talk is about slide rules in a particular medium, the movies. Pictures of slide rules in the hands of famous people or cute advertisements were shown at former IMs, but the pictures here are also moving, and with sound! With a number of examples, we will show how and why slide rules are used in movies, their type, from documentary to feature films of various types, even animation movies, and what role they play in the story and the characterization of people in the movie.

  An initial, shorter version was shown at the 2012 IM at Bletchley Park as kind of an after-dinner-speech, but now we have a number of new and interesting snippets for this presentation to end the first day of IM2026. It will be fun!

In this session we first take a look at the past, back four centuries, at logarithms, the mathematical base for slide rules. The old discussion Delamain Then we direct our eyes the oposite direction, looking at evolving 'artificial intelligence' in an experiment about slide rule knowledge already present in some AI systems, and an approach how such knowledge could be structured and handled for a user.

• Mirifici Logarithmorum Canonis Re-Constructio — Reconstructing the Mathematics of John Napier’s Logarithms
  Simon van der Salm (NL)
  Napier and Jost Bürgi were the first mathematicians to develop systematic methods for calculating logarithms. Napier was the first to present his method and its underlying principles in detail in his 'Constructio'. The lecture explores how Napier's original ideas can be understood and reconstructed in the language of modern mathematics, shedding new light on the mathematical foundations of his work.

• What Invention? Whose Invention?
  Jose G Fernández (ES)
  A new reading of Delamain, Forster and Oughtred publications, filtered with slide rule and patent expertise, provide new conclusions on what was invented and who were the inventors of the first slide rules after Gunter's invention of the logarithmic ruler for navigation. Working only on statements without the emotional load that impregnated these publications, Jose G. Fernandez shares a new technical-only verdict for the slide rule collectors community. This short presentation starts from what has been discussed in Groups.io mainly by Andreas Poschinger and Ted Hume, but with the participation of many others.

• Slide rules and AI
  Jacques Perregaux (CH)
  The article presents initial experiences with AI in searching for information about a slide rule manufacturer. It then compares three AI providers based on specific questions about slide rules and evaluates the results. Finally, the findings are assessed.

• GraphRAG-enhanced Visual Ontology of Slide Rules
  Wolfgang Irler (IT)
  A calculator collector uses AI to analyze slide rule history. He shows Neo4j's GraphRAG is more than a chatbot backend. Instead, it can be considered a visual ontology for side rule knowledge.

Session D            See programme schedule for local times.

• Insights Into the Rules of George Washington Richardson
  Mike Syphers (US)
  George W. Richardson produced inexpensive metal slide rules from his home in Chicago at the beginning of the 20th Century. Earlier accounts have been told of advertisements of his products in the magazine 'Popular Mechanics'. Searches through the magazine's earliest issues help to ascertain a time line of his slide rule production. Links to J.J. Clark and the I.C.S, and other insights into the development of Richardson's business are also presented.

• How Many Analons? — A K&E Serial Number Study
  Mike Syphers (US)
  A brief report on the discrepancy of the generally perceived rarity of the K&E Analon slide rule and the serial numbers on specimen found, which imply a much higher number of them actually produced.

• The Oughtred Society Award and Fellowship
  Karl Kleine and Bob de Cesaris

• Past, present, and future of the yearly International Meeting (IM) and the International Workshops (IW)
  Karl Kleine (DE)
  Short presentation of crucial data about these events together with some thoughts about essential ingrediences for their success in the past and challenges for the future. Preparation for the business meeting following.

• IM business reports and discussions
  • reports of the slide rule organizations: Oughtred Society, UKSRC, KRING, RST
  • discussion of shrinking memberships, in particular the number of active members, largely due to age, health problems, and ultimately death, and the urgent need of volunteers to help run the organisations and its activities
  • future of International Meetings and the end of face-to-face meetings,
    most pressing the currently open question of the organization of IM2027
  • future of International Workshops, more than just identifying / decyphering "unknowns", but using the workshops also for the exchange of practical experience in slide rule collecting
  • future of slide rule publications

Slide Rule Auction            See programme schedule for local times.

organized by the Oughtred Society. It has its own   auction web page