GWMC15 - GreenWater Magic for the Canon 15mm and other wide angles.
The GWMC15 is a GreenWater Magic filter designed to fit into the filter holding slot on the rear on several on Canon's wide angle lenses. These include the Canon 15mm FE, 14mm, 16-35mm Mk1 and 17-40mm (this filter does not fit the Canon 16-35mm Mk2). Sensibly Canon has made this filter the same size on all these lenses. The filter measures approximately 31x31mm. The filter is square although you may wish to trim the leading edge corners so it slides more easily into the filter holder. Note that Sigma lenses made for Canon cameras take smaller rear filters (approx 23x25mm) - although it would be possible to cut down a larger Canon filter to fit a Sigma lens. Note that green waters are usually darker than blue tropical waters and filter photography in these conditions often involves long exposures.
As this filter is made from the GreenWater Magic formula the photographer must set the white balance manually (using Custom White Balance) every time they change depth by a few metres during the dive - this is usually done by taking a reference photo and then setting the White Balance using Custom to that photo (see your camera manual for more). This filter is designed specifically to work with the white balance of a modern digital camera in blue to blue-green waters.
A single GWMC15 costs £22 and a pack of three filters costs £35.
Magic filters are designed for available light underwater photography. The GreenWater Magic works from 4m down to at least 22m (70ft). This filter does tend to render green waters more blueish. All our filters are optical quality polyester gels, manufactured for us, to our recipes, by one of the world's leading filter companies. All Magic filters are supplied with detailed instructions.
Sample photo taken with the GreenWater Magic Filter: