P08456: Underwater Light/public/
Underwater Lighting Considerations
OverviewThis page will provide information on the behavior of light under water.
Meeting with Dr. Emmett Ientilucci (Center for Imaging Science)
- Light intensity fall off is exponential but predictable in water.
- Beer's Law relates the transmission of light through
a substance and the concentration of the substance, and
also between the transmission and the length of material
that the light travels through.
- http://en.wikipedia.org/wiki/Beer-Lambert_law - General overview of the formula and the terms involved in it.
- Water Visibility Components:
- Water "Case" 1, 2, 3 describes conditions from very clear water (Open Ocean) to very turbid water (Genesee River), with 3 being the most turbidt and cloudy-least visibility.
- CDOM - Color Disolved Organic Materials
- Suspended Solids
- Alternate Types of ROV lighting
- "Laser" Rastering System. Scans the area with a small point of light very quickly.
- CCD Cameras have a responsivity range of wavelengths
that depends on the semiconductor
- This responsivity will drive the optimal wavelength to use for lighting in addition to the Beer's law concerns.
- Black and white makes lighting easier in that a pure digital count of reflected light and allows tailoring of lighting for best illumination.
- Light and Camera sharing path to source.
- Scattering Phase Functions cause light to scatter in universal or preffered directions.
- Scattering is wavelength dependant (ex. Blue light scatters more, blue sky)
- Depending on the Phase functions for water (did not have specifics at this time) this could be a nonissue or a large issue.
- Particulate Illumiation is also affected by path sharing.
- Wavelenghth does not change with transmission through pure water/air. It can only change if the light is re-radiated (phosphorous materials).
- Gave us contact information for an water imaging
specialist at RIT.
- Dr. Anthony Vodacek
Meeting with Dr. Anthony Vodacek (Center for Imaging Science)
- There are specific curves that characterize the way
light behaves in water, the most critical influences on
absorption are the dissolved solids, chloryphill, and the
water itself is the main contributing factor for
refraction is the water, and the CDOM in the water.
- All water (fresh of seawater) absorbs an increasing amount of light at the upper range of the visual spectrum-from about 625 nm and up. Because of this, Infrared light will only penetrate a few feet at best, regardless of the conditions.
- The chloryphill absorbs a large abount of the blue light at the lower end of the visible spectrum, and reflects a large amount of the green light (why photosynthesizing organisims look green).
- The CDOM, which is made up of dead organic material, reflects mostly yellow light (why murgy water often looks yellow).
- Suspended solids are dense materials, that mostly reflect light, and do not contribute to the overall absorbtion of light.
Light attenuation in water caused by particulate matter. Courtesy of Department of Biology East Carolina University Greenville, North Carolina
- The majority of scarrering in water is caused by Rayleigh scattering, the light is scattered equally; and by Mie scattering, which is dependednt on the size of the particle in relation to the light wavelength.