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Things remained messy. After the 110 V came 115 V, 120 V and 125 V, while 220 V was
followed by 225 V, 230 V and 240 . Not every maker mentioned the voltage on their lamps. For
example, on the lamp for the Bauer Pantalux of 1934 you would read: 5 A 375 W. So you had to
know that Watts = Volts × Amps. In this case the voltage was 375 ÷ 5 = 75 V. After 1945 we saw
more standardization, the ampere classification was no longer used: just the voltage and wattage
were recorded. The factories gave their products numbers but then you discover that Philips gave
this number depending solely on the wattage of the lamp. If you ordered the 6152 C you got a
500 W lamp but which voltage? This you also had to specify in your order. Even the wattage was
sometimes a problem. The 110 V, 500 W lamps were already hard to get in
the thirties but, when Noris announced an eight-millimetre movie projector
with a 220 V 500 W lamp in 1950, the first series was delivered with a
Philips 220 V 400 W lamp because the 500 W was not yet in production.

In addition to the lamps above, a line of shorter lamps with the bayonet
Ba15s base was developed. The projectors became smaller, but all these
apparatuses had problems with the heat and the
Fig 6. Centering card amount of light that could be used. To use the
slide light that did not go directly to the lens, a mirror
was introduced behind it. It reflected the light back into the lamp and
that caused more problems because the lamp itself became overheat-
ed. The answer was to insert a slide between the filament and the lens
to centre the reflected light. This slide had a hole in the middle and
you had to put the plastic lens cap on the lens to see what you were
doing when you wanted to fit it. With 8 mm projectors you had to use
a magnifying glass that projected an image of the filament onto your
screen.

With the Ba15s base the distance of the bayonet base to the centre of
the filament was standardized to 35 mm. Manufacturers also wanted Fig 7. 33 v 100 w lamps in
to reduce the voltage of the lamp but that was not a new idea. The the Visolux projector.
small lamps in cars with their low voltage became the ideal for many years. Pathé used a small
12 V 0.5 A lamp in the first 9.5 mm projectors. Already in the thirties Philips produced an 11 V
100 W lamp. In 1947 they produced 33 V 100 W lamps for slide projectors, but most of the
projector manufacturers did not follow them.

Noris had one type for the schools, the Delita, and the Dutch Visolux was a school projector with
a reserve lamp already installed.

The breakthrough came through changing the filament: the wire was now wound into a small
plate as large as an 8 mm movie frame. Engineer Georg Malek,
the designer for Eumig, was so enthusiastic about this 12 V
100 W lamp that he built an Eumig mov-
ie projector around this lamp. It became
the legendary Eumig P8; more than
1,250,000 of them would follow. You
can also find this lamp in slide projectors
such as the Leitz Pradolux. This needed
another centering slide, for now you had
to adjust the reflected light over the top Fig 8. Centering card
of the original glowing filament.
The Eumig P8 for the 12 V 100 W