UNDERWATER PHOTOGRAPHY is about getting close to your subject. The less water between you and it the better, because water filters and spreads light, and even the clearest water contains particles that diffuse light.
Besides, the light of your flash is the deciding factor in most underwater photos, and it seldom extends further then a few metres, so playing paparazzi is a waste of time! Underwater photo-graphers are in reality limited to two fields, close-up or wide- angle, and both require you to be close to your subject.
So get close, and get the focus right. With modern digital cameras, automatic exposure is adjusted for light conditions on land. You can keep the camera on Auto under water, but youll miss an abundance of exciting possibilities.
Taking a photograph is to register light, whether through exposing a chip or a film roll. Too little light will cause an underexposure, too much an overexposure. Three factors determine the degree of exposure, and if you understand them you can simply customise the camera adjustments for different situations.
Factor one, light sensitivity, is measured in ISO amounts. This derives from analogue camera film and relates to the amount of light with which a film can function. A film with a low ISO needs a lot of light and vice versa. Digital cameras usually choose their ISO adjustment automatically (ie 50 or 100).
Depending on the brightness, several more expensive digital cameras allow you to adjust the ISO manually. With an ISO of, say, 800, you find more digital noise in the photos - they become more coarsely grained. Adjust the ISO as low as the brightness allows.
Factor two is aperture, with a diaphragm regulating the size of hole through which light passes. Aperture-sizing seems entirely illogical. For example, 8 is a small hole that allows very little light to pass through, while 2 is a large hole through which it pours. But the number of the aperture size is actually the denominator of a fraction, so a half is bigger than an eighth - right
In dim lighting, the camera will automatically choose a large aperture (a small size). The aperture size decides even the depth of field. The smaller the aperture, the larger the depth of field, so the larger the carelessness margin with regards to clarity. Choosing the smallest aperture possible makes it easier to keep the details of your subject in focus.
Aperture sizes between analogue and digital cameras are not comparable. A digital cameras tiniest opening is often an 8, on an analogue camera typically 22, because of the difference in size between a film frame and a digital chip.
Factor three is shutter speed, which determines for how long the chip or film is exposed to the light. A slow speed (1/10sec) is used in poor light, as in deeper waters, but in bright light (ie on a white sandy beach in high sun) a fast shutter speed of 1/1000sec is used.
Short shutter speeds are recommended to freeze quick movements - when, for example, you are trying to capture fish darting past you at high speed, or sunbeams dancing down from the surface. With a shutter speed longer than 1/30sec, it can become difficult to hold the camera still enough, and you risk blurry photos.
A cameras various factory settings (portrait, landscape, close-up, night or others) are the makers recommendations on possible combinations of light sensitivity, aperture and shutter speed in several common situations - but on land. Your camera should give you the possibility to adjust manually for any underwater conditions you may encounter.
Underwater photography demands discipline when it comes to pre-dive preparations and after-dive care and maintenance. The tiniest sand particle or hair can flood your camera, ruining thousands of pounds worth of photo equipment in the blink of an eye.
The determining factor is the O-ring. The same type is found in both regulators and dive torches, holding the housing tight and keeping the camera dry. Exact procedures for care of the seals are given in instruction manuals, but bear in mind that water leaks in a camera housing almost always occur as a result of haste.
So take your time, be thorough and methodical and, if you dont have time to give your camera the care and attention it requires, dive without it!
A photo may be perfectly exposed, yet a total technical disaster if not in focus.
The sun is one of the most important compositional elements in a wide-angled photo and you may have to make numerous attempts before finding the right balance. A cameras built-in exposure program can easily be fooled, resulting in a black picture.
A poorly focused picture, despite any other qualities, always ends up in the bin. No one likes blurry images. The subject on which you are zooming in has its largest depth of field in the wide-angle end of the zoom area. The closer to the zoom limit you get, the more thorough you must be in adjusting your sharpness.
A digital cameras auto-focus doesnt always function well in water. It can be fooled by a subjects low contrast and particles floating in the water, and eventually you will need to focus manually to get a sharp photograph.
The cameras Achilles heel lies in that moment between you pushing your finger down and the shutter opening. Between the auto-focus and the strategic calculations which the cameras tiny computer must execute, a time-lapse is inevitable.
With practice, you will soon learn to initiate the photo slightly ahead of time.
Does your cameras automatic installation have a setting marked Aperture Priority You choose the aperture and the camera chooses the shutter speed. The smaller the aperture you choose, the longer the shutter speed the camera will choose. This method works well as long as the camera does not choose a speed slower than 1/30sec. If you dont have Aperture Priority, try the Landscape setting. This usually gives a smaller aperture - but beware of those slow shutter speeds.
Lets say you have space on your memory card for 100 images. You take one photo each of 100 different subjects and are probably overjoyed if you find a single good image when your card is full.
Say, instead, that you take 10 photos of 10 different subjects. Its still 100 shots, but you will most likely have at least one good picture of all 10, and can trash the rest.
You cant fully trust what you see on your cameras LCD screen. The screen doesnt always reveal whether the photo is clear and correctly exposed, which is why you should take several photos with different adjustments either side of the standard setting.
This bracketing can be achieved by adjusting several different strengths into your flash (if it works); by varying the distance between your flash or dive torch and the subject; by adjusting your flash angle; by changing the exposure settings (aperture, shutter speed, ISO); or by varying the view between portrait and landscape, where appropriate.
The combinations are endless but so is digital film - the memory card can be used as many times as you want. Load the photos you want onto your computers hard disk, empty your card and start over again.
Look at photographing as a two-stage process. In the water, take clear, correctly exposed photographs with interesting subjects. Then edit and fix them up on your computer - we will cover this process next month.
if your subject has an eye, make this the point of focus
a small aperture often results in a dark background - fine if you want your subject to stand out
black and white photos taken with long shutter speeds can give impressive results
use of balanced light - the foreground lit with a flash, the background by natural lighting
1 Practise with your camera on land - both naked and with housing in place - until youre familiar with the positioning of the essential knobs and buttons. Read the manual thoroughly. You should be able to turn the flash on and off, shift between close-ups and regular distance photographs, and choose between an automatic program or a manual setting in your sleep!
2 Allow your subject to fill the viewfinder, then check the background for unwanted fins or bubbles.
3 Purchase the largest memory card you can and take lots of photos in different ways.
4 Dive with a buddy who has the patience to indulge your photographic pastime.
5 Analyse other peoples pictures - what makes them good or bad Try to work out how they were taken: Deep or shallow Large or small aperture Flash or natural lighting Wide-angle or close-up
6 Underwater photography requires luck. The more you dive, the luckier you will become.
7 The camera saves information about the aperture, shutter speed, white balancing etc in every photo document. Minimise these either on the LCD screen or later on your PC, to help you study and learn.
8 Never jump or roll into the water with camera in hand. The sudden pressure change can disturb an O-ring. Ask a bystander to pass you the camera once you are in the water, and similarly pass it out of the water at the end of a dive.
9 Accept the limits of your camera and dont waste time taking photos beyond its technical abilities.
10 Have fun!
World of Pixels lesson 1
Into first gear lesson 2
Time to get wet lesson 3
Fixes and tricks lesson 4