"Magic!"

Today I finally found the time and inclination to use my "Magic" gel filter. This is a coloured gel that fits on the front of the lens (I use a screw in UV filter to hold it in place.) The particular hue of orange-red was designed by Alex Mustard to restore the colours lost to absorption of light in the water column.

Water absorbs reds first, and blue-violet last, resulting in a washed out appearance with increasing depth. Typically underwater photographers use strobes to create balance, white light at depth, but while this works well for some subjects, large objects become impossible to light in this way. The best you can do with strobes is to carefully select what part of the scene to light.

Sea Viking wreck, foreground illuminated by strobe.

The magic filter uses a different technique to restore colour. Instead of adding balanced light to restore colour, it filters out the blue light, reducing it to the same level as the red light that has already been filtered by the water, resulting in an overall balance. Its not an exact match, and some of the balance has to be done by the camera's white balance function, but the results can be dramatic.

Sea Viking, this time shot using ambient light and Magic filter.

Needless to say, no solution is perfect. Some subjects benefit greatly from the controlled lighting strobes provide, a strobe is just as bright at 100ft as it is at 30ft, and doesn't suffer from cloudy days. When exposure relies on ambient light making its way through a significant depth of water, and then a filter, I start struggling with shutter speeds falling and motion blur, still, for some subjects, it can be a startling difference.

Shark Cage with Strobe.



Shark Cage using filter.

These Horse-eye Jacks are almost impossible to photograph using a strobe thanks to their reflective bodies. Here the filter let me get close and show them as a diver would see them.