Underwater photography tips
Australasian gannet above and below - Popes Eye, Port Phillip
Before contemplating underwater photography you must be
comfortable in the water. Great buoyancy skills and the ability to dive without kicking up sand are essential. You must also
be able to dive one handed, the other hand will be holding the camera.
It also helps if your dive sites have calm water, lots of co-operative
critters and great vis, which is unusual in sub-temperate southern
Australia.
The basics
Move in as close as possible
Move the flash away from the camera
Exposure
Use flash power and position to adjust forground exposure
Use aperture to adjust overall exposure
Use shutter speed to adjust background exposure
More advanced tips
Better lighting
Aperture priority with manual flash
Manual focus with framers
Pre focus
Black and white underwater
Move in as close as possible
If you can't reach out and touch your subject you are too far away.
I'm sure you don't believe me but if you want bright, sharp, colourful images you must get as close as possible to your subject. This is the major difference between above and under water photography.
The composite photo of an Australasian gannet above shows the difference between air and water. As soon as you go below the surface, brightness, warm colours and visibility are lost.
Water is 800 times denser than air and consists of microscopic
particles like water molecules, plankton, silt and a stack of other
things you probably don't want to know about. Water molecules absorb
warm colours and all the other particles cause haze and backscatter.
You have to consider that you're also photographing all that water, plankton, silt and crud in front of your subject.
For sharp colourful results you must minimize the amount of water between the camera and subject.
This principle is the same for all
underwater photography, whether using the cheapest disposable or the
most expensive housed digital SLR. Most underwater photos are taken at a distance
of less than 1m from the subject, close-up shots are usually closer
than 50cm and macro shots are closer than 20cm.
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distance 1.5m, no flash
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distance 30cm, no flash
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Move the flash away from the camera
The second big step to getting great underwater photos is to buy an external flash, giving much better control over lighting.
Water molecules, plankton and suspended particles act as a blue/green filter that increases with distance through the water. This filter effect reduces red, then orange, then yellow light leaving green and blue.
If you want to capture bright
colourful images at depths below a few meters you need to replace
this lost light by using a flash. However, the flash will also
illuminate all the particles in the water, causing backscatter (bright
blurred spots in front of your subject).
If you are just using the camera flash then backscatter will be a problem. Good clean shots
will be impossible unless you are in crystal clear water or very close to your subject.
Moving the flash further away from the lens will avoid illuminating
particles between the camera and subject and may produce more
interesting lighting.
A good starting point is to move the flash the same distance away from the lens as the subject distance.
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backscatter
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less backscatter
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If your setup is fully automatic all you can do is aim the camera, push the button and hope for the best. You may be lucky and capture the odd decent shot.
However if you are serious about underwater photography you need to take control and use manual exposure settings. It's not as difficult as it may seem. Eventually you will have a couple of standard settings for macro and wide angle.
Here are my Compact Camera settings: ISO 100
Macro: Shutter speed 125, Aperture 7.6
Wide angle: Shutter speed 60, Aperture 4.0
Here are my SLR Camera settings: ISO 200
Macro: Shutter speed 125, Aperture 22
Wide angle: Shutter speed 60, Aperture 8.0
I then make adjustments starting from these proven settings.
I usually leave the aperture alone and adjust the flash power to expose the subject correctly and adjust the shutter speed to expose the background how I want.
These adjustments are explained in more detail below.
Use the aperture to control overall exposure
You actually have two light sources underwater. The first being flash and the second being ambient (sunlight penetrating down from the surface).
By adjusting the aperture you adjust the overall exposure of both the flash and the ambient light.
Compact digital cameras usually have apertures from 2.8 (largest aperture) to 8.0 (smallest aperture)
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aperture f/3.3, 1/30th sec
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aperture f/5.2, 1/30th sec
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aperture f/8, 1/30th sec
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| Smaller
apertures such as f/22 (SLR), and f/8 (Compact Digital), give more depth of
field. Larger apertures like f/2.8 give shallower depth of
field.
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Use flash position and power to control foreground exposure
By turning the flash power up or down you can lighten or darken the subject (or foreground exposure) without changing the background exposure. Moving the flash closer to or further away from the subject achieves the same result.
My Inon Z220 can be adjusted from full power to -5.0 stops.
More recent models can give Auto flash exposure (S-TTL) by mimicking the camera flash. This usually works for macro photography but not so well for wide angle.
Less flash darker subject
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Correct flash power
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More flash lighter subject
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Use shutter speed to balance background exposure
Shutter speed only affects exposure due to ambient light. This is
because the flash duration is usually much shorter than the shutter speed.
When
you take a shot, the shutter opens, then the flash fires in a very short
burst, then the shutter closes. So adjusting the shutter
speed does not alter the amount of flash delivered.
This means you can set the flash and aperture to correctly expose the foreground subject
then adjust the shutter speed to make the background go from black
through to bright blue/green. The choice is up to you.
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Fast shutter speed
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Mid shutter speed
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Slow shutter speed
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Flash sync speed
With
the Nikon D80,
speeds faster than 1/250th cannot be used with flash because the flash will only expose
part of the scene. This is because the shutter blinds never fully open
at speeds faster than the "Flash Sync Speed" of 1/250th. Check the Flash
Sync Speed of your camera to determine the fastest usable shutter
speed. Most compact digital cameras can use all shutter speeds with flash. This is one of the advantages they have over SLRs
Advanced techniques
External strobe positioning
Most single flash heads sit above and to the left of the lens. This is
not always the best position. Much of the time you will be lighting up
the fish's tail or the back of the nudibranch.
Moving the single flash to center above the camera will improve the
lighting to some extent. However, the most flexible and creative method
is to disconnect the arm and hand hold the flash in the best position.
You can light up faces or give more dramatic cross lighting which will
bring your subjects to life.
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flash above left
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flash above right
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Two strobes
Single strobes will always produce dark shadows, which is not always a
bad thing. However, if you want total control over lighting then you
need two strobes. The second strobe is used to produce more even
illumination by adding light into the dark shadow areas.
Of course an extra strobe costs more, weighs more and is harder to
handle underwater. It's best to master the single strobe before taking
this next step.
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Aperture priority with manual flash
This is a great technique for photography in shallow water with lots of ambient light.
With the camera on aperture priority, you select the correct aperture
for the flash and the camera calculates the shutter speed depending on
the ambient light. I find it's a good idea to dial in some "minus EV" (1/2 to 1 stop) for a
darker background.
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Manual focus
If you're totally frustrated with slow or impossible auto focus why not
revert back to Nikonos methods. Manual focus gets rid of the autofocus
delay making it easier to shoot moving fish, at low light levels, and
even at night.
Wide angle
Using a wide angle lens and f/8 (smallest aperture on compact cameras) set the manual
focus on about 0.20m (experiment to find what works for you) and
everything will be focussed from about 15cm to infinity.
Macro
With the Nikon Coolpix 5000 I could set manual focus to 0.07m and long zoom, then move the camera forward until the subject is in focus on the screen.
This method is a little difficult because you need good eye-sight and no bright light on the screen to be able to pick when it is sharp.
Using framing prongs
This is an easier method for macro manual focus. Using framing prongs of the correct length and width guarantees sharp results as long as you can keep the subject between the framers.
Click here for a macro framer design giving horizontal coverage of 30mm.
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Pre focus
I often try to photograph seadragons or bluedevil fish
under ledges in the deep shadows. Auto focus does not have a hope in
this situation unless you shine a bright torch on the subject.
However you can use a temporary form of fixed focus which means you don't need the torch.
Pull back in to brighter ambient light and half press the shutter to
focus on something bright. Hold the shutter lever there and move back
under the ledge, line up the subject at roughly the same distance as
the bright subject and shoot.
You will have greatest success with wide zoom and small apertures when using this method.
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Black and white ambient light photography
If you're photographing wrecks you will not be able to light up the whole
wreck with your flash so most of your images will be illuminated only by ambient
light. This means they will be predominantly low contrast monochrome blue or green images.
Wrecks look great in black and white and you have much more scope for
enhancing contrast without worrying about retaining realistic colours.
Many other subjects with little colour and good tonal range may look
great also.
Digital images can be desaturated and the contrast adjusted either at the time of shooting or on the computer.
It is also so much easier to use the camera on Auto exposure and not have to worry about flash settings for a change.
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Colour capture
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BW, contrast increased
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