# Dial Colours Underwater?



## Stan (Aug 7, 2003)

I was speaking to my best buddy Mark today and he was wondering what colour Orange and Yellow dials appear when underwater?

I didn't have a clue but I told him I knew some guys who might.























Over to the experts.


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## namaste (May 8, 2003)

I'm not an expert, but a member of the scientific comity of the CMAS...









So here's some info before Nalu or Jase jump in!!

from the web, some interesting facts, copyright Deep-Six:

The light spectrum is well known. "ROY G. BIV" is an acronym used to remember the colors from one end to the other. From left to right the letters stand for: Red, Orange, Yellow, Green, Blue, Indigo, and Violet.Â A mixture of all the colors makes white light. Â That is, if one were to take 7 flashlights, each of which was giving off one of the listed colors, and shine all the different colors on a white wall, the spot of light would be white! A white light, therefore, gives off all the colors.

Â Â Â Water acts as a selective filter. If one were to suspend a white light above the surface of a tank of water that was 1000' deep, the colors from the white light would be filtered out selectively one-by-one. It is gradual. There is no abrupt interface. For example, most of the red is gone from the light after 10 feet. Some of the orange is gone. Less of the yellow is lost, etc. At 25' most of the orange is gone. At 35' most of the yellow is gone. This continues through the spectrum until all that is left is violet light and that fades out after hundreds of feet. So, at the bottom of this 1000' tank of water there would be little or no light!

Â Â Â Selective filtration creates conditions that make diving interesting. If a diver is bleeding at 60', where there is no red light, the diver bleeds a greenish-black blood. Taking a photograph at 30' would result in most objects appearing green, blue, violet, or black. Taking the same photograph with a flash (white light) would reveal startling colors that were not seen by the diver. Remember, the selective filtering by water occurs in any direction. So a camera's flash will lose most of its true color effectiveness after a distance of as little as five feet! That is because the light would leave the camera, hit the object 5 feet away and then return to the camera. In that 10 foot travel distance most of the red would be gone and the orange would be diminished.

Â Â Â Neon colors do not loose their color like spectrum colors do. This author has video photographed a red stripe on a wet suit turn to black as a diver descended. Neon red and "hot pink" still were sending out bright color at 100'. That is because they fluoresce. Ultraviolet is found after violet on the spectrum. It is invisible to humans. It, like violet, goes to extreme depths. When a neon color is struck by the invisible ultraviolet it glows.

Â Â Â At the other end of the spectrum is the red light that is filtered out by water rapidly. Beyond the red light there is a part of the spectrum that humans cannot see but can feel. It is infrared. (In the far red.) It is also known as heat. That is the energy that one can feel standing in front of a fireplace even though all the hot air, smoke, and gases are going up the chimney. Heat energy travels at the speed of light. You thought red light had trouble going deep in water. Infrared cannot penetrate 1mm! So you might wonder how the oceans get warm if heat cannot get down into the water? It's not the heat from the sun that makes the oceans warm. It is all the colors that are selectively filtered by the water. Â They are "captured" by the molecules of water and are converted to heat energy because the molecules are made to move faster.


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## ESL (Jan 27, 2004)

So... what colour would they appear then?


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## Nin (Jul 16, 2004)

I haven't dived with a yellow or orange dial watch but some of my kit is yellow & orange, and it invariably looks grey at depth - until of course you shine a torch on it.

Nin


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## Nalu (Nov 28, 2003)

Pieter has provided a great explanation of how light *transmission* works under water He also is spot on about why fluorescent colours work. He's given me an idea about using UV light supplementation in my UW photos: quite a few ocean flora and fauna fluoresce









The second piece of the puzzle is of course how our light *reception* works under water. We have two 'types' of vision because we have two classes of light sensing cells in our retinas: rods and cones. Rods supply *scotopic* vision, IOW grayscale vision and are the most sensitive cells. Rods are what enable us to see in low-light conditions, albeit in black and white. Cones supply *photopic* vision, IOW colour vision.

In the absence of colour input (i.e. the wavelengths corresponding to ROYGBV), our retinas revert to scotopic vision. Of course, as Pieter has stated, there are still _some_ colour wavelengths at SCUBA depths, so coloured diver dials appear as variations of gray/green/blue.

So the Irish answer for Mark is "What 'colour' do orange and yellow dials appear in the dark (low light)?"









All this is why I'm always on about about divers that use red on the dial and poor contrast dials whenever the subject comes up (usually over at TZ-UK).


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## Stan (Aug 7, 2003)

I think Mark should take up diving and find out for himself, bless him.
















Thanks lads.


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## namaste (May 8, 2003)

Thanks Nalu!


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## jasonm (Nov 22, 2003)

Ive got a nice group shot of my Orange Monster, Seiko Tuna Can and the Citizen Eco 300M at 23M ....But youll have to wait a few more days as Im still in Nassau


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## redmonaco (Nov 29, 2004)

ESL said:


> So... what colour would they appear then?
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## abraxas (Oct 21, 2003)

jasonm said:


> Ive got a nice group shot of my Orange Monster, Seiko Tuna Can and the Citizen Eco 300M at 23M ....But youll have to wait a few more days as Im still in Nassau
> 
> 
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john


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