underwater videographer course | underwater video technique | white balance

White Balance

White balancing video cameras underwater

Everything you shoot is simply light. Radiated light or reflected light

Loss of Color Underwater

Water acts as a filter

Cuts out red spectrum first

Show chart of colour loss with depth

Loss of red with distance as well as depth

Add depth plus distance from subject

Use shot of Padangbai reef to illustrate loss of red with distance/depth

Manual White Balance versus Automatic White Balance

Which cameras allow manual white balance (3CCD etc.)

Which housings all manual white balance

slate

glove

hand

white fin

the reef in general

white or grey

Colour Correction Filters

Internal screw-on

Internal flip

External

Glass or plastic

UR-Pro

pic of UR-Pro

Magic Filters

pic of Magic Filters

Wetpixel thread! - http://wetpixel.com/forums/index.php?showtopic=16970&st=120

Make a decision between trying to make everything look the same as it would if it was lifted to the surface, or accepting that it's blue/green. Nobody is "correct".

Available Light versus Artificial Light

The human eye and brain "calibrates" itself to an extent to changes in the colour temperature of the ambient light. So in a room filled with warm tungsten lighting the brain compensates for the yellowness and allows us to differentiate the full range of colours in the room. Under fluorescent lighting we compensate for the "cool" light and feel that whites are indeed white and not pale greenish blue. Similarly underwater, although the red has all but gone at depth, my brains can still distinguish the red fish from the blue. Unfortunately cameras do not do this automatically. Under tungsten light everything looks yellowish, under fluorescent light everything looks bluish, and under water everything quickly becomes a washed out monochrome blue/green.

[b]In theory[/b] the result will be a bit warmer with the fin, assuming the slate is closer to the camera.

When trying to understand this stuff, it helps to think of water as a very thick green/blue weakly-coloured filter. It also helps to consider the distance light travels from the light source to your subject, plus the distance that light travels from the subject to your camera after it has reflected off your subject.

The loss of red in light depends on the total distance the light travels. For example if you're shooting with available light (i.e. daylight, not electric lights) the total distance the light travels is the distance from the surface to your white balance surface, plus the distance from that white balance surface to your camera. This is the "water column" that the light travels through. If you're at 20m depth and your fin is 1m further away from your camera than a white slate would be, this means that the light is travelling 21m when using a fin, as opposed to 20m with a slate. i.e. just 5% more which is just about negligible. However if you're at 5m depth then this extra distance is 20% more (6m not 5m) and therefore more significant.

Personally I prefer to white balance on the palm of my hand these days. The result is great and it's convenient i.e. I usually have a good idea where my hand is (unless I'm deeper than 55m on air... then it's debatable).

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