Antique Mechanical Exposure Meter

[RMD]

Make your own calculator :

http://www.squit.co.uk/photo/exposurecalc.html

 

[Ralph Javins]

Good morning;

If you want to ponder what we all may have forgotten over the years in terms of non-electronic systems to perform intricate calculations for us, take a look at the Antikythera Device or Antikythera Mechanism, an ancient Greek astronomical computer and calendar.

 

[Lightproof]

In this conext, you might also be interested in the work of Tatajana van Vark:

http://www.tatjavanvark.nl/projects.html

She actually can build things like that - and a bit more if you take a closer look at her "harmonium". She also replicated the Antikythera mechanism. Awesome work if you ask me.


And, as mentioned before, don't forget to take a look at the Curta: http://www.vcalc.net/cu.htm

 

[Samuel Hotton]

Hello Steven,
You are quite correct about the calculator having inputs for colour of walls and floor, and the use of ordinary and ortho emulsions.

Film speed *is*accounted for by the widget with the four pointers. They are in Hurter & Driffield scale. There are several different H&D scales depending on the country and time period. My Posographe appears to be in British H&D from1920. So I calculate a Ordinary rapid 70 H&D to be about ASA 1, the Extra Rapid H&D 200 is about ASA 5-6, the Ultra Rapid H&D 450 is about ASA 11-12.

A point of interest is that this calculator was tweaked for lighting conditions at 45 degrees North Latitude. This is interesting as Paris is 48 degrees and Venice is 45 degrees. Most interesting, why?

The Posographe works and works well! I have used is for exposing paper negatives in old wood and brass cameras at ASA 6 = H&D 200 with great success. I wish a modern version could be made today. And it could.

Have fun and may all your shots be Cameos.
Sam H.

I've been having a really good close look at this Kaufman Posographe.

Printing off the pictures as A4 and then googling some of the French into English helped a lot

From a photographic point of view, it calculates exposure from Month, Time of day, Scene, weather and colour & lighting of the subject. Interior views use colour of light and colour of walls, I think (I haven't translated that bit, yet) and the 'zones' are the distance from the window.

There seems to be an emphasis on colour presumably because this would have made a big different in the days of 'ordinary' and 'orthochromatic' emulsions.

One thing that is missing is film speed! This is accounted for by the output display unit (the oblong brass widget) having four pointers on it. these are designated Ordinary, rapid, extra rapid and ultra rapid. I think they refer to specific plates and the spacing between them isn't even. They could be the equivalent of something like 2, 8,16,32 ISO, maybe? (Would Ultra Rapid have reached ISO 32 in the 1920?)

It seems to be it is a pretty comprehensive calculator that takes into account most factors and I reckon would have worked well, with the four types of plates it was intended for in the 1920s.

 

[Old-N-Feeble]

Want want want want want want want want want want want want want want want want want want want want want want want want want!!!

 

[mono]

I have one!! I have one!!! I have one!!!!!!!!!

 

[E. von Hoegh]

Remember; no two lightmeters ever agree, and I doubt this thing was as accurate as anyone saying "cool" gives it credit for.

If it worked that well, there would be similar devices that worked for trig rather than the 1 dimensional slide rule of days long gone.

There were analog mechanical computers made for directing torpedoes, bombs, antiaircraft fire, and naval artillery... they worked as well as the man using them programmed them.

http://www.glennsmuseum.com/bombsights/bombsights.html

 

[E. von Hoegh]

I have one!! I have one!!! I have one!!!!!!!!!

I HAD one. Like the imbecile I occasionally am, I offed it... along with a pristine Heyde's Aktino Photometer in the original box.

 

[snapguy]

Weston

And I thought my Weston light meter with Weston (not ASA) film speeds was olde.

 

[pentaxuser]

I have one!! I have one!!! I have one!!!!!!!!!

Worth keeping, Folker. Show it to some kids. If they don't show an interest in how it works or want to play with it then I despair for the future of engineering as we once knew it. Not everything worth having is on a screen and virtual

pentaxuser

 

[mono]

I certainly will!!
My brother-in-law bought it at the Dorotheum in Vienna and gave it to me as a present.
He knew that I am an oldfashioned analogee ;-)