Thread: Diving video
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Old 3rd June 2018, 17:07   #37  |  Link
StainlessS
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Quote:
Originally Posted by tormento View Post
It could be nice to have that reverse water color absorption formula and use diving computer log to apply it.
Presumably absorption would be based on depth of viewed object, and distance to camera from it (something like depth*depM+dist*distM).

Perhaps some large white object fixed at some depth eg 10m, and something tracking distance from the object up to say 100 m.
Repeat every 10m depth (up to 10,994 meters, the Mariana Trench would do nicely).

EDIT:
Quote:
I only surmised
Arh, so its not called the Orange-fin thingy.

EDIT:
Quote:
Noticed feint magenta tinge to the blues after posting. This one, a bit less:
I rather liked that one, nice.

EDIT: This gets some hits: "red spectrum absorption of sea water":- https://www.google.com/search?q=red+...ient=firefox-b

EDIT:
http://www.waterencyclopedia.com/La-...the-Ocean.html

Quote:
Light Penetration.

A certain amount of incoming light is reflected away when it reaches the ocean surface, depending upon the state of the water itself. If it is calm and smooth, less light will be reflected.

If it is turbulent, with many waves, more light will be reflected. The light that penetrates the surface is refracted due to the fact that light travels faster in air than in water. Once it is within the water, light may be scattered or absorbed by solid particles. Most of the visible light spectrum is absorbed within 10 meters (33 feet) of the water's surface, and almost none penetrates below 150 meters (490 feet) of water depth, even when the water is very clear.

Quote:
Light Spectrum.

Water selectively scatters and absorbs certain wavelengths of visible light. The long wavelengths of the light spectrum—red, yellow, and orange—can penetrate to approximately 15, 30, and 50 meters (49, 98, and 164 feet), respectively, while the short wavelengths of the light spectrum—violet, blue and green—can penetrate further, to the lower limits of the euphotic zone. Blue penetrates the deepest, which is why deep, clear ocean water and some tropical water appear to be blue most of the time. Moreover, clearer waters have fewer particles to affect the transmission of light, and scattering by the water itself controls color. Water in shallow coastal areas tends to contain a greater amount of particles that scatter or absorb light wavelengths differently, which is why sea water close to shore may appear more green or brown in color.
Quote:
MEASURING LIGHT TRANSMISSION

Scientists have developed several different methods and instruments to measure light transmission in water. The simplest measurement method involves the use of the Secchi disk, a white plate about 30 centimeters (12 inches) in diameter. It is fastened horizontally to a rope marked in meters. The disk is then lowered into the sea, lake, or other waterbody. The depth at which the disk is lost to sight is noted using the rope markings. This provides a rough estimate of the depth of light penetration.

A more sophisticated device for measuring light transmission is the nephelometer, which measures the scattering of incident (incoming) light by particles in the water. The optical backscatter meter and light scattering meter work in a similar fashion by projecting a light beam into the water. A detector on the instrument measures the amount of light that is scattered back into it.

The transmissometer measures light attenuation, or the sum of scattering and absorption of light in sea water. It projects a beam of light of a known wavelength over a known distance, and the data may be used to calculate the percentage of light that is transmitted at a certain depth.

The a-c meter has separate sensors to detect absorption of light by particles and total light attenuation. It functions in a manner like that of a transmissometer.
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Last edited by StainlessS; 3rd June 2018 at 17:35.
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