L as lumen

In the Tonga archipelago with René Heusey and his lighting assistant on the set of one of the episodes of the series “Carnets d'Expédition”. At the time (barely 10 years ago) these were the revolutionary and “all new” HDMI lights!

Definition

Under water, sight is life, as we have already said. But in the darkness of the depths and even more so in the absolute darkness of the caves, the use of artificial light is necessary. What could be more banal than a diving lamp? And yet...

Synonymes

Lighting | Light | Power | watt | Candela | Candle

Starter

I'm going to talk to you about a world that people under 60 can't know: that of underwater lighting, in those heroic times when you couldn't see a thing...

Redundancy requires, we took several of these sources of lighting to compensate for possible but very frequent breakdowns which, underground, would have been fatal. With the autonomy in breathed air, the power and duration of our lighting was indeed fundamental. You have to have progressed for a while, hand on the wire, in the total darkness of a drowned gallery to understand what I mean… Power, we didn't talk about it, it was so ridiculous (incandescent bulbs powered by batteries!) and as everyone was housed in the same boat, only counted the number of lamps used together. It was only with the generalization of halogen bulbs that we began to compare the powers expressed in “Watts”.

fiat lux

A misleading value since the unit Watt (W) – according to the engineer James Watt – measures the power P of an electrical component. But it was used as a standard for two hitherto proportional measures: The electrical consumption of the bulb and therefore the power of its luminous illumination. Knowing that these bulbs had a deplorable performance and that a large part of the power used was dispersed in heat. It was like that...

Since we swim in units, we must also evoke the Lumen, Candle, Luxury, not to mention the “foot candle","candlepower" and others "foot candle“Anglo-Saxons who definitely do everything upside down…

The Lumen indicates the amount of radiation visible to the naked eye per second. This is the current standard for “LED” lighting. While the Candela encompasses the amount of light emitted for any direction. It is a unit of measurement used to represent a quantity of lighting, or a luminous intensity. It is sometimes said that the Candela is the equivalent of the intensity of light emitted by a candle. True, but not specific enough: what type of candle are we talking about? For what length of wick, what type of wax? Nothing to wax? Neither do I. We do not understand anything? I agree. Also, Candela has nothing to do with the US Secretary of State. Condoleezza Rice who was specialized in media insights…

The Lux (Lx) is a unit of measurement rather used for artificial light sources. It is directly related to the physiological perception that we have of light. It quantifies the quantity of visible light received on a given surface. 1 Lux = 1 Lumen on an area of ​​1 m². Thus in the advertisements of solar panels for which the power supplied depends on the quantity of light perceived. This unit can also be used to determine the value of global solar radiation. The measurement of an illumination in Lux is carried out by a Luxmeter, whose detection element is a photodiode with spectral sensitivity similar to that of the “average” human eye. That's done !

During a fairly short period of transition, halogen bulbs were dethroned and replaced by hdmi bulbs more fragile and precious than the diamond without having its resistance and which had to be transported at our risk and peril, outside the headlights, air safety obliges...

Big Blue

We then saw the appearance of a new generation of underwater lighting based on “LED” diodes. Considered at first glance as gadgets or toys for adults, this technology ended up giving birth to monsters of power for insane autonomy, the consumption of this type of "lamp" being up to ten times less important than that of bulbs. "incandescent" or "halogen" with a much better efficiency, generating for example much less heat which makes them usable outside the water. The halogen headlights of yesteryear, the weight of an anvil, also had the “toaster” function…

To get an idea of ​​the Watt equivalent of these little monsters, just divide the number of lumens announced by 10. Thus, the little amulets big blue that I have in test at the moment, which display a power of 15000 lumens, represent a halogen equivalence of 1500 W, i.e. two old and enormous Subatec headlights associated together, such as the ones we took to shoot some sequences of the film "The Black Water” in the giant siphons of Cocklebiddy Cave en Australia… The impression of lugging around, from all points of view, a cast iron radiator.

As for the autonomy available today, it is simply not comparable… Minutes have become hours. Not to mention the color temperature (more or less warm) and the angle of illumination (wide brush, narrow brush…) so many factors that greatly influence the “power” and the final autonomy of the lamp… These lightings big blue are imported into France by Custom Diving Systems friend Yannig Charles.

Main course

As we have seen, long before the arrival of halogen headlights, we only had to explore the siphons of scanty battery-powered lamps of barely a few watts, in particular the emblematic yellow “Aquaflash” which lit by screwing its head on a thread drowned in silicone grease. Complicated or even impossible operation in depth because of the pressure. However, we took at least one helmet with two of these lamps on, and another off, as a backup, attached to the forearm.

Light turn signals

It was in this outfit that I dived for 9h30 and reached the end of the Hole Madam Batch. Except that it had been hundreds of meters since I had to give up the use of one of my headlamps which had gone out (one of the customary “false contacts”) and now the second one began to flash, according to the position of my head, while I inventoried the pile of black rock briquettes from the terminal hopper of siphon 9…

I could fill books with these conquests of darkness, armed only with these battery-operated “flashlights”, moving lights in the eternal night. Still it would have been necessary to tell the time when my brother Eric, crossing me at least sixty meters in the wells of the big Goul de Tourne en Ardèche during my peak at -97 m in the air, told me with his twisted finger on the helmet that I was crazy: I was going up, glued to the wall, in the improbable orange luminosity of the filaments of my headlamps, a sign some discharged batteries!

Dessert

The first siphons were crossed (in 1922) by Norbert Casteret who dived naked and in complete darkness, into the eight-degree waters of the Pyrenean caves!

Later, he will pass the first liquid locks with candles and matches rolled in a bathing cap. We can easily imagine him, at first, naked and shivering in the flickering light of a wet candle subject to drafts... Before discovering the famous clay statues in the Montespan cave.

 

Finally, with his son Raoul he will continue his underwater incursions, this time using willow branches tied end to end as Ariadne's thread. The lighting will consist of a lighted electric lamp enclosed in a glass canning jar...

 

Kerosene lamps under water!

In the same vein, the lamps of the first divers worked with oil, suspended on the submarine refloating site from the surface and connected to the surface by two pipes, one connected to a small air pump and the other allowing the evacuation of burnt gases. Another smaller kerosene lamp was sometimes connected to the diver's back regulator for its compressed air supply.

It was in 1865 that Rouquayrol et Denayrouze experimented with electrical energy for underwater lighting, despite the rapid wear of the coals which were used to generate an illuminating arc. But they know it's the future… The first models see the light of day with their robust “steampunk” look. For example, this heavy battery-powered lamp, made of bronze, which dates from the 1950s.

See you soon for a new definition of Scuba Bécédaire. The irreverent lexicon of diving, but not only. Because sometimes ...

Francis Le Guen

Café

A few things to consider when choosing a dive light.