Matt BlazeWho needs a light meter or a histogram? Behold the Posographe, an insanely beautiful 1922 mechanical computer for calculating exposure time based on aperture, time of day, sky conditions, and other variables.
French lessons not included.
Ryan PietzBasically: you move the six sliders along the edges to correspond to your aperture and shooting conditions. That moves the exposure slider (which you don’t touch) to the correct shutter speed. There’s an absurdly complex system of internal levers that somehow doesn’t disturb anything other than the exposure slider when you adjust each input.
You can read more about it at https://www.nzeldes.com/HOC/Posographe.htm
I found mine on ebay a while back.
Update on the Posographe: there are four shutter speed pointers, depending on which of four emulsions you’re using. Based on the “sunny 16 rule” (set for f/16, portrait in the open directly sunlit, with a blue sky at noon in summer), I’d estimate the four supported ISO equivalents to be roughly 3, 8, 25, and 50. ISO 50 would have been super fast film for 1922, so this seems about right.
The "sunny 16 rule", for you autoexposure kids, is a rule-of-thumb for estimating correct exposure: On a bright sunny day, with the subject in the sun, use an aperture of f/16 and a shutter speed that's the reciprocal of the ISO value. So for ISO 50 film, you'd use 1/50th of a sec.
loums@mattblaze
What's film?
What's film?
Ian Littman@mattblaze And you can use this for taking pictures of the moon as well.
Catch is a lot of phone lenses are pretty fast these days so you have to adjust the formula heh
@ian Though for the moon it's the f/11 rule (because of the somewhat retroreflective surface of the moon being at a slightly off angle, as I recall)
Mark@mattblaze I usually shot 200 ISO film which was f/8 at1/200 which is how I remembered it. Kodachrome 64 was the lowest I went in ISO which required some math and guestimating.
Graham Webster@mattblaze with no willingness to download the thing I was delighted to find this guts image along with what looks like a really cool emulator https://www.animatedsoftware.com/elearning/KaufmannPosographe/index.html
Steve Bellovin@mattblaze Way back when, I took many properly-exposed pictures without a light meter (an archaic phrase) and no auto-metering, just by reading the leaflet that came with every roll of film (another archaic phrase).
BunNICKula🇨🇦That piece of paper got worn out, when switching from 100 to 200 to 400 film.
I loved taking and developing b&w photos of the deep woods, sans flash, of light and dark, greys and water trickling. It was magic.
@intothewestaway @mattblaze When I do more artistic photography, I prefer B&W. These days, when I do mostly bird photography, color is better, though there are exceptions, e.g., this one from 1.5 years ago.
Coincidentally
@ct_bergstrom has some lovely feathery pictures just posted.
Stephan Neuhaus@mattblaze Amazing, this kind of rule of thumb also exists in other languages. The German almost-equivalent is "Die Sonne lacht, nimm Blende acht" (roughly, "if the sun is shining, use f/8"), even though this says nothing about the exposure time. I guess the Germans weren't a fan of Group f/64.
Natanael ⚠️@mattblaze is there any way to get to see the insides? X-ray?
bmaz@mattblaze Am fascinated by that thing.
ewhac@mattblaze We may need a short video to illustrate its operation...
gladiola@mattblaze This is awesome. Thanks for posting this. I've had a Kodak book of cardboard wheels for about 30 years. I cannot imagine the maximum nerding that would have occurred if I had seen this earlier in life.
@gladiola I remember that book!
Michael@mattblaze this is seriously amazing! The sort of knowledge and skill gone into designing this is amazing
Adam Shostack 
@mattblaze if only you knew someone who liked to take pictures of complex and obscure machines! 😇
@adamshostack At least the exposure will be correct.
@mattblaze @adamshostack Well, that assumes that you coat your camera's sensor with the proper emulsion.
Simon Zerafa