Gossen Ombrux exposure meter.
The Ombrux exposure meter was first introduced on the fair at Leipzig in 1933.
was the first photoelectric photographic exposure meter made by Paul Gossen and
marketed to the international market.
Their actual first meter was named
Photolux however the name of this meter changed very shortly after
introduction to Ombrux. With
this meter he founded the Gossen company for light measuring equipment which is still existing.
The high price of a selenium element was a big problem to market the Ombrux meter for an commercial interesting price. However Paul Gossen
solved this problem by deciding to start a production of 100.000
exposure meters, so he guaranteed the manufacturer Electrocell in Berlin
an order of 100.000 selenium cells, in this way Electrocell was able to
deliver the selenium cell to Paul Gossen at a price of 7.50 Reichsmarken.
At the time of the fair, Paul Gossen was able to offer
the Ombrux for a price of 29.50 Reichsmarken excluding the leather case. The question was
only if the
time was right to offer the photographic market a meter instead of the
old ways to make the exposure.
At the same time, Weston brought a meter
on the market in the USA but this was a very expensive equipment. On the same
fair in Leipzig was another company who brought a likewise meter on the market,
Metrawatt a company from Nurnberg and founded by Dr. Siegfried
the Ombrux, photographers could measure actually the light instead of
estimate the light value by experience, use of the not so reliable
aktinometer or use of tables like the one made by
Paul Dette. The Ombrux was
made for photography while his
counterpart the Blendux was made for cine purposes.
The meters from the type Ombrux always have a scale with exposure time
value in seconds. The types do differ, some have only the plate / film
speed in Scheiner were others have the Scheiner scale combined with DIN
value. In most cases the value is 23 Scheiner, 15~16/10 DIN. The film
speed seems relatively low but in that time this was the regular filmspeed.
The measuring element is a selenium photovoltaic cell and the big lens on
the front was taken from a flashlight manufactured in that time in
Germany. The case holds some aluminum plates with correction tables in
DIN and the older German value: Scheiner.
Also known is a version made for Leica, with Ombrux f. Leica printed on
the scale. (see photo). The big difference is here the adoption of the
scale to the Leica aperture and exposure time values.
With a little formula, the Ombrux can be used as a light meter instead
of an exposure meter. By taking the reciprocal of the value and
multiplying this with 50 you will get the light value in lux. See on the
bottom of this page for an example of this formula.
Except for Photography, the Ombrux was also used in the agriculture
sector like in forestry, to measure the
amount of light in the woods for growing young trees.