And for my photography friends, I present..... the Posographe!

[Nittersing]

Designed in the 1920s to assist with camera settings.



And here is a short (3min) video showing how it works.

[CaliforniaPeggy]

1. How incredibly detailed and fascinating!

I have never seen anything like it. Someone was very clever in making this. Seems as though it would take some time to set up properly.

Thank you for sharing this, my dear Nittersing!

[Nittersing]

4. Isn't it fun?

I've never seen anything like it before either!

[2naSalit]

2. I like it!

What a cool device.

[Biophilic]

3. What a very clever gadget.

People really are amazing.

[Silent Type]

5. An app with real tactile feel.

[Nittersing]

6. Haha, you're right! It's an app!!! nt

[ornotna]

13. There's an app for that app

https://apps.apple.com/us/app/animated-antique-posographe/id1488545400?platform=iphone

[Silent Type]

14. Good find. I might have stuck with photography 50 years ago with something like that.

[usonian]

15. Oh that's crazy.

Program's author:

https://www.animatedsoftware.com/elearning/KaufmannPosographe/index.html

The Kaufmann Posographe is a fascinating mechanical contraption which was used by photographers in the early 20th Century to set their exposure times. Back then exposures were measured in seconds, and everyone in the picture had to freeze ( "pose" ) for the entire time. Film plates were expensive and difficult to handle, so do-overs were avoided as much as possible. Over 100,000 French versions of the Posographe were sold alone, as well as tens of thousands of English-language versions. (Although this program is in English, the far more common French Posographe is depicted.)

This animation was originally created based on an article in the Oughtred Society's bi-annual journal, Spring 2019 issue Kaufmann Posographe (pdf), and then the lead programmer purchased an antique Posographe in order to make more accurate measurements and higher resolution photographs, to check the placement of some hidden connections, and lastly, to test the accuracy of the model against an actual Posographe. It's very close!

Kaufmann invented and patented several versions of the Posographe and a couple of other related mechanical contraptions. The mathematical theory behind how the Posographe works was conceived around the same time, and Kaufmann apparently had a number of correspondences with the mathematician who invented the theory. Although the theory is not explained here, the math behind the Posographe is illustrated with connecting lines, colored brass plates (or not, if you prefer!), circles indicating intersecting positions of the pieces, and various additional ways of exploring "under the hood."

From the paper (recommended)

Mechanism:


Schematic:


Facebook page (no login required)
https://www.facebook.com/posographe.kaufmann

[Think. Again.]

7. What a fantastic mechanism! Wow.

[rsdsharp]

8. That looks like it ought to be strapped to the forearm of an NFL quarterback.

[erronis]

9. Reminds me of a trip to the Smithsonian 1876 Cententennial Exhibition

Around 1996 I took some co-workers from overseas to roam through the rooms of the old original Smithsonian Castle. We admired the craftsmanship of the devices that were displayed. Such fine details on the brass and glass and woodworks. We all said something to the effect of "They just don't make things like that anymore."

Then we wandered over to the Air and Space Museum. On display were models of the first moon rover - built out of plastics and foil and seemingly light-grade metal. And we realized that they do make things like that - just different and for the purpose.

[Warpy]

10. I used to set it at f-11 and forget it

back in the days of B&W film and going out for a day of random shooting because anything over or under exposed could be handled at the enlarger.

That's an interesting artifact, though. It would have come in very handy for people using commercial processing.

[Bernardo de La Paz]

12. WeeGee said "F/8 and be there." . . . . nt

[Bernardo de La Paz]

11. Fascinating. An analog computer

I noticed that the output moved little for some inputs and a lot for other inputs. So the ratios and leverage would have taken quite some time to get right because the inputs are all interconnected.

Could perhaps be calculated, but it is a 5 variable input problem. Some are reciprocals or followers. The scale on the front can be adjusted too (during development).

Thank you for bringing this to us!