WHICH URPRO FILTER?
Use the URPRO SWCY filter with available light in shallow blue-green tropical fresh and salt water. (SW = Shallow Water ~ CY = tropical blue green water) The SWCY filter is ideal for ALL video, digital, still, and cine camera systems. This screw-mount filter is available in optical glass only, and in most popular sizes.
Use the URPRO CY Filter with available light, and/or electronic flash in tropical blue green fresh and salt water. Ideal for ALL video, digital, still, and cine camera systems. This filter is available in optical glass and optical plastic in most standard sizes. (CY = tropical blue green fresh and salt water)
Use the URPRO GR filter with available light and/or electronic flash in green algae fresh and salt water. Ideal for ALL video, digital, still, and cine camera systems. This filter is available in optical glass and optical plastic in most standard sizes. (GR = green algae fresh and salt water)
These URPRO filters are distinctly different and cannot be interchanged.
WATER IS A NATURAL FILTER
Full spectrum colors exist underwater at great depths. Without a URPRO color correction filter, these natural underwater hues become “distorted/changed” when seen by the human eye, or attempts are made to record images using film cameras or electronic cameras. This “color shift” happens because water is a natural filter altering the wavelengths of light as it passes through the water. The deeper the water, the greater the color shift.
The proven URPRO filter technologies restore the underwater hues by "neutralizing” the different and dominant false masking colors as light passes through the water. Using sunlight only, URPRO filters allow the natural colors –already there— to be seen by the eye and recorded electronically or captured on film
The URPRO SWCY optical glass filter is scientifically designed to insure optimal light transmission characteristics. This filter corrects colors using natural sunlight in shallow water and is designed to be used with ALL video, digital, still, and cine camera systems.
SWCY EFFECTIVE DEPTH RANGE
The URPRO SWCY filters are also designed for use with natural sunlight at depths slightly below the surface, to a maximum of 25 feet/4 meters.
[For color correction at greater depths, use the URPRO CY filters. The URPRO CY filters are designed to be used at depths between 12 feet/4 meters and 50 feet/17 meters, or greater depths, depending upon local conditions.]
VISUAL APPEARANCE OF URPRO SWCY FILTERS
The URPRO SWCY filters visually “appear identical” to the URPRO CY filters. However, these two URPRO filters are distinctly different and cannot be interchanged.
SWCY FILTER POSITION
This URPRO filter can be positioned in front of the underwater housing or inside of the housing. The filter can also be mounted on the front of the prime lens of the camera or wide-angle adapter. URPRO filters can also be “sandwiched between” the prime lens and wide-angle adapter.
SWCY EXPOSURE FACTORS
On the surface, the URPRO SWCY filter will have approximately a 1-F/stop light loss. When using cameras with automatic exposure capabilities, there is NO exposure compensation required because automatic systems calculate the light loss.
When a separate light meter is used to determine the exposure, it is suggested the light meter’s ASA/ISO Setting compensate for the light loss. (See Practical Examples, next column.)
ASA/ISO 200 original film rating
= ASA/ISO 100 “adjusted” film rating caused by the SWCY filter light loss
ASA/ISO 400 original film rating
=ASA/ISO 200 “adjusted” film rating caused by the SWCY filter light loss
IF no light meter is used, a one F/stop light reduction must be calculated into the exposure to prevent under-exposed images. Under all circumstances, an “exposure test(s)” is strongly encouraged.
MIXING DIFFERENT LIGHT SOURCES
Do NOT use the URPRO SWCY filter with electronic flash. Light sources different than natural sunlight will produce unsatisfactory colors and images.
Under certain conditions, it may be possible to mix diffused 3200 Kelvin video light with sunlight and the SWCY filter. Under all circumstances, a “color balance test(s)” is strongly encouraged.
When mixing sunlight and 3200 Kelvin video light, the sunlight must be the main light source while the video light provides “fill light” to the darker parts of the scene. The video light should be directly above the center of the camera lens and pointing slightly downward to help simulate natural sunlight.
CLEANING/CARE OF URPRO SWCY FILTERS
The URPRO SWCY filters are made of high quality optical glass and are mounted in filter rings made of black anodized aluminum. When imaging in saltwater, the filters should be thoroughly rinsed with fresh water and gently dried with a soft absorbent cloth. Although he URPRO optical glass filters can break, they are difficult to scratch and should always receive the same degree of attention given to other premium optical products.
UNDERWATER FILTER DISTANCE
SWCY FILTERS ONLY
Photographically and visually, the natural blue green (cyan) effects of the water dominate reds, oranges and other warm colors. This happens because water is denser than air, and because water also acts as a natural filter. Consequently, the deeper an underwater imager goes beneath the surface, the greater the colors are “filtered out” of the spectrum.
To select the correct URPRO filter for the proper depths, and to compensate for the loss of colors, the depth of the water must be added to the distance between the camera and the subject. This combination of numbers yields the Underwater Filter Distance.
Using natural sunlight only, the URPRO SWCY filter yields the best colors when used just below the surface of the water, and when the camera to subject distance combination is less than 25 feet/8 meters.
Use the following formula to determine the correct Underwater Filter Distance for the URPRO SWCY filters.
IF the Underwater Filter Distance is greater than 25 feet/8 meters, use the URPRO CY correction filter which is designed to restore the color spectrum for depths between 10 feet/3 meters and 60 feet/20 meters.
SWCY Filters are ideal for ALL still, video, digital and cine camera systems.