Fontenelle archives 5

[Pecole]

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This curious ETRIN came - as expected - with a Leica I, FODUA rangefinder and brown cardboard twin cassette holder, but also, in the detachable case, a BEWI "extinctometer":

The detachable case is especially interesting and sophisticated : it has definitely been ptroduced with and for the ETRIN, to which it attaches with both a metal "tongue" slipping in a leather fixture on top, and a 90º switching fastening button entering a corresponding metal reinforced split protruding from the ETRIN's bottom. When interviewed, Leitz people coldn't give another explanation than "Many things were made on special order in these times".

[luigi bertolotti]

Yup, very interesting accessory bag: un-coded, for what it seems... but even if it was an on-request item, i suppose that leather and even knitting are the same as ETRIN... Leitz was great on details, at that times...

[aesop]

...truly fascinating piece(s) - any further details on the "extinctometer"? I have no idea what it is.

[luigi bertolotti]

...truly fascinating piece(s) - any further details on the "extinctometer"? I have no idea what it is.

 

Extinctometers were light meters that, instead of electrical measurement of light (with cells which generate power proportional to light intensity - selenium - or resistors whose resistance is proportional to light - CdS) used a simple optical device... in practice a sort of graduated ND filter you look through...when the light is "extincted" you read out the corresponding density - proportional to light intensity. They were made for years by several vendors before and after WWII : much less precise and sensitive than electrical meters, but very simple to build and reliable, having no circuitry at all.

[Pecole]

...truly fascinating piece(s) - any further details on the "extinctometer"? I have no idea what it is.

 

Here are two photos of the BEWI extinctometer "Special for Leica camera" . you looked through the eyepiece, rotated the body until light disappeared, thed read the measure.

[aesop]

Here are two photos of the BEWI extinctometer "Special for Leica camera" . you looked through the eyepiece, rotated the body until light disappeared, thed read the measure.

 

 

...thanks, Luigi and Pecole - you learn something new every day.

 

How precise (or imprecise) were the readings? For instance, were the readings tight enough for correctly exposing transparencies? And am I correct in assuming this device could only take reflected light readings?

[gyoung]

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...thanks, Luigi and Pecole - you learn something new every day.

 

How precise (or imprecise) were the readings? For instance, were the readings tight enough for correctly exposing transparencies? And am I correct in assuming this device could only take reflected light readings?

 

Not very precise, the longer you looked the lighter it looked as your eye accomodated and the iris opened up.

You would have more success with sunny 16 IMHO

 

Gerry

[giordano]

Dunn and Wakefield (authorities on exposure and metering) began their work at a time when extinction meters were sold and used, and investigated them thoroughly. They say that with care and practice and after calibrating the readings you get to the film and processing you use, "reasonably consistent readings are possible within, say, plus or minus two stops of the average" (Exposure Manual, 4th edn, p.84).

[luigi bertolotti]

Dunn and Wakefield (authorities on exposure and metering) began their work at a time when extinction meters were sold and used, and investigated them thoroughly. They say that with care and practice and after calibrating the readings you get to the film and processing you use, "reasonably consistent readings are possible within, say, plus or minus two stops of the average" (Exposure Manual, 4th edn, p.84).

 

...+ or - 2 stops, and only after "practice and care"...