Another Old Exposure Aid

[xpatUSA]

From time to time, I've posted pics of a Hurter and Driffield slide-rule - usually in the context of modern exposure metering - a sort of "how it used to be" comment.

Today I found this amazing contraption:



Image from the link: https://www.nzeldes.com/HOC/Posographe.htm

Posted for interest - click the link for more info.

I'm always interested in other old exposure or photographic aids - feel free to append a post to this thread!

As Harold MacMillan said in the '60s - we've never had it so good ...

[pschlute]

Cracking bit of engineering

[dje]

That’s brilliant Ted. How on earth did he design those linkages at the back? Computer simulation? Slide rule perhaps!

[xpatUSA]

That’s brilliant Ted. How on earth did he design those linkages at the back? Computer simulation? Slide rule perhaps!

Hi Dave,

"Kaufmann’s Posographe was patented in 1922"

More here:

http://www.oughtred.org/jos/JOS2019-...28-1_36-43.pdf

So not computer simulation ... I think they had slide-rules back then, though ...

... and he did use Nomograms for calculation.

[Tom Barry]

Fantastic, like something out of the 19th Century.

[xpatUSA]

A much better picture can be seen here:

https://www.andreruiter.nl/posographe-by-kaufmann/

[William W]

What a great tool.

It took a lot of effort pulling my high-school French to the front of my brain to read it all.

***

Tit Bits – for those inclined to trivia and emotionally charged historic minutia

‘Aperture Zones’ - from 1900.

Glaringly obvious (and particularly interesting) was the (French) recognition of the “English” Uniform System, (for Apertures), which was (apparently) adopted (or it seems at least discussed at length and in detail) at the 1900 Photography Conference and associated soirees, held in Paris.

See in the image, under “DIAPHRAGME” (English = diaphragm – modern day meaning ‘aperture’)
(On the tool scribed - “Angleterre uniform system USN Congres international de 1990”)

The Numbers 1 to 128 (GP, a.r^n where a=1, r=2, n=0,1,2,3,4,5 …) were noted as ‘diaphragm zones’. I think this 'standard' did not survive very long: I have only seen this referenced once or twice before and I can't now remember where those references where.

What I found additionally interesting: - in the ‘aperture zone’ numeral “1” appears F/4.5, which is a stunningly super fast ½ Stop under the F/5 in that same ‘aperture zone’.

Oh the lenses were super fast back then...

***

At that Conference -


“Photographers coming down steps with cameras”, Paris, 1900.
Frances Benjamin Johnston (1864-1952),

Repository (Original Print and Digital Image File): Library of Congress Prints and Photographs Division Washington, D.C. USA. (Open Section access)
This enhanced digital file is reproduced here, for educational and commentary purposes.

WW

[William W]

^ Additional noteable trivia Frances was a woman Photographer.

[xpatUSA]

The Numbers 1 to 128 (GP, a.r^n where a=1, r=2, n=0,1,2,3,4,5 …) were noted as ‘diaphragm zones’. I think this 'standard' did not survive very long: I have only seen this referenced once or twice before and I can't now remember where those references were.

Also interesting is that in the second link I posted for a better picture -it only went up to 64 for the "English" numbers.

Remarkable that you found a picture related to that Conference, Bill. Well done!

[William W]

Also interesting is that in the second link I posted for a better picture -it only went up to 64 for the "English" numbers.

Remarkable that you found a picture related to that Conference, Bill. Well done!

I am reading the second link now, thanks: Note also the second image allows for a super fast F/2.5 aperture camera lens - AND - 1/1000s Shutter Speed (not 1/400 as in the first image) - these facts imply that there were at least two versions of the tool. ?

I already had the picture. I (we) visited Washington in 2019, the Library of Congress is overwhelmingly fantastic. I was researching historical pieces to investigate for about a year before we left AUS.

My Wife is an History buff, much more catholic in taste than me - I tend to limit my brain to Architecture and Photography, with a touch of Music here and there: however on tour with my Wife is fantastic - my own personal "Universal History Guide".

Anecdote - we were in the Rotunda, National Archives Museum and (US) school kids were on excursion: one of them asked their teacher a question on the Bill of Rights and then additional questions regarding the Constitution. The teacher seemed kind of stuck for detail, so my wife offered to take over... a good ten minutes later, the 'Teacher' (later found out was Deputy Principal) thanked my Wife for the lesson and asked (tongue in cheek) if she would like a permanent job - she said she already had one back home and that 'lesson' was just a bit of light fun.

It was great visit, we stayed until we were kicked out at closing time.

WW

[dje]

How about an exposure slide-rule like this one, patented in 1888!



The fundamentals of exposure haven't really changed much!

The full article can be found here.

Dave

[xpatUSA]

How about an exposure slide-rule like this one, patented in 1888!



The fundamentals of exposure haven't really changed much!

The full article can be found here.

Dave

Yes, that is indeed the one I mentioned in post #1, Dave. Love that patent date ...

... and thanks for the link, duly bookmarked.

[dje]

Yes, that is indeed the one I mentioned in post #1, Dave.

Sorry Ted, i missed that bit. I'm trying to work out how the slide-rule was used:

The interface between the middle slider and bottom fixed section is where you set the film speed

The interface between the the middle slider and the top slider is where you set the shutter time and scene illumination

But where is the reference point for the Aperture setting at the top of the top slider? EDIT : I think it’s the white chart at the back!

I must be missing something obvious?

Dave

[xpatUSA]

Sorry Ted, i missed that bit. I'm trying to work out how the slide-rule was used:

The interface between the middle slider and bottom fixed section is where you set the film speed

The interface between the the middle slider and the top slider is where you set the shutter time and scene illumination

But where is the reference point for the Aperture setting at the top of the top slider? EDIT : I think it’s the white chart at the back!

I must be missing something obvious?

Dave

From your link:



My best guess is:

Put in the card which seems to be for a latitude about 50 miles north of London.

Set the card vertically - apparently end of June early July.

Set the lower slider to loaded plate speed - "20" in this case.

Set the desired aperture on the upper slider against a time of day line on the card, say f/20 against 9am/3pm ... I'm guessing that's local solar mean time.

Now pick a light quality on the lower slider and read the exposure time just above it on the upper slider.

In other words, I don't think they used to set the shutter time back then because that is what the Actinograph is designed to calculate -and the scene illumination is what you observe so as to read the appropriate exposure time.

Probably no coincidence that from "very dull" to "very bright" is exactly 2EV ...

[dje]

Thanks Ted, that all makes sense.
Dave

[William W]

Yes, Ted, I concur. The calculator's task is to find the necessary exposure time:

a) knowing the date, time of day and film speed
and then
b) choosing the aperture to use

The printed card will slide up and down relative to the wooden calculator. This is done first to select the date period.

In the image the date period chosen is about 13th June to 3rd July.

WW

[Cantab]

A fascinating thread.

Ted, I look forward to your next equipment oddity!

[rpcrowe]

Being too poor as a teenager to afford a proper exposure meter, I used several exposure aids, ranging from the instruction sheets that came with the film to slide rule (both circular and linear) exposure aids. I even had a device that I viewed the scene through that had a series of transparent squares of different densities with numbers. The first density through which I was able to see the number determined the exposure...

Then with one of my first paychecks from the Navy Reserve (which I joined a month after I was 17 years old) I purchased a Weston Master II meter. I was in hog heaven but when I attended the Navy School of Basic Photography in 1959 (at 19 years old) I learned and became versed in the "Rule of Sunny Sixteen" which actually worked quite well with black and white film...

[Cantab]

I even had a device that I viewed the scene through that had a series of transparent squares of different densities with numbers. The first density through which I was able to see the number determined the exposure...

Richard, did this device actually work in practice? I'd never heard of it. I'm sightly younger than you; my first recollection of exposure aids were the instruction sheets that came with film.

[xpatUSA]

Richard, did this device actually work in practice? I'd never heard of it. I'm sightly younger than you; my first recollection of exposure aids were the instruction sheets that came with film.

I think it be an 'extinction meter', Bruce:

http://camera-wiki.org/wiki/Exposure...inction_meters
.