When taking sunlight pictures, you must use a lightmeter. It can either be built in the camera or, as is the case with the system used by Danielle here, it can be seperate. Picture taken with ambient light only.
For this shot, Danielle used ambient light. Picture taken close to the surface with a medium speed film (ISO 100-200) can be done without a flash. However, you should take precautions to seperate your subject from the background.
In photography, light is everything. The most basic lighting system you can use is natural light, sunlight, what photographers often call available or ambient light. Let's find how you should work with it.
Suitable subject and light measurement
Not all subjects are suitable for ambient light photography. Large wrecks, objects located close to the surface and those with high contrast are your best bet. Any subject that does not stand against its background should be avoided.
Once you have found your subject, try to use an upward angle if it is possible.
In topside photography you can follow simple rules to determine proper exposure without the use of a lightmeter. Underwater however, it is a different story.
There are so many variables affecting light levels at depth that you cannot, without considerable experience, precisely guess the amount of light reaching your subject. You need a lightmeter.
Photography gods and marketing people have acknowledged this problem and most cameras have built-in lightmeters, many of them even automatically measure light level and adjust camera settings accordingly.
However, a separate hand-held lightmeter is an invaluable tool in u/w photography. Unfortunately, Sekonic, the only company that manufactured a submersible u/w lightmeter, ceased the production of its L-164 Marine Meter recently. There are some leftovers in stores but new units are not manufactured any more. Look around for used units and if you are serious about underwater photography buy one.
We also suggest that you learn how to take available light pictures first by using your camera in its manual mode (if it has one). This will help you better understand how the camera works and will prove helpful later on in your "photography career".
Measuring light level is quite simple. If you work with a separate lightmeter or a Nikonos camera, select 1/60 second as your basic shutter speed. Then, aim the lightmeter/camera at your subject. With the Nikonos, you turn the aperture knob until the chosen shutter speed is the only number glowing in the viewfinder and, bingo, you have selected the appropriate aperture. The Motormarine II EX only has an underexposure warning LED. With this camera if you see a red light in the viewfinder it means that you do not have sufficient light. When it glows, move the aperture control knob to a lower number (which means a larger opening, i.e., more light reaching the film).
If you work with a separate meter, read the aperture suggested by the pointing arrow and adjust the aperture knob on the lens accordingly.
One universal rule to follow: Try to aim your meter close to your subject. This prevents false readings from the surrounding water/objects.
Sounds too good to be true? Right, life is never that simple. A lightmeter sees the world in gray, it tries to optimize exposure according to an "average gray reflectance". Simply put, this means that your light measuring device cannot take into account the fact that your subject reflects more or less light (i.e., bright surface vs. dark surface). You should interpret your meter readings.
If your subject is dark and sits on a highly reflective background such as sand, take a meter reading and open up your aperture by one half to two f/stop over the figure given by the device. If you are shooting a bright subject on a dark background, you should take the opposite route (use a smaller aperture than the meter suggests).
Take pictures at different apertures (a technique called bracketing) to make sure you have the right exposure. We will get back to bracketing techniques in another article.
Silhouettes
Silhouette pictures are one of the best applications for the ambient light technique and they catch the attention of the viewers. When taking your reading for a silhouette shot, avoid aiming the lightmeter/camera directly at the sun. Point the meter at an angle of approximately 45 degrees off the sun's position. This will give you properly exposed surface water and, if you add a diver in the picture, he will appear as a sharp silhouette.
You can do the same with fish schools, coral formations or wrecks.
Automatic settings
Cameras like the Nikonos, the Motormarine and housed systems can be used in automatic mode. In this case you select the aperture and the camera automatically sets the shutter speed.
This "point-and-shoot" technique may be useful, but the meter can be fooled by the background or some other factors. Since the camera cannot interpret the reading, there is no compensation.
There is however a technique to compensate. It involves playing with the ISO dial on the camera and, in our opinion, is more complicated than the manual technique shown above. We will cover this in another article.
Tips for better photography
Mastering available light photography is an important step in your learning process. Use ISO 100 or 200 print film and practise this technique. Analyse your results and take notes. It will pay off later.
Here are some basic rules you should follow:
Use a light meter;
Interpret your meter readings;
Work in shallow water;
Use upward angles;
Use a minimum speed of 1/60 second to prevent blurred images. Do not hesitate to use higher speeds if your subjects are moving fast;
Make sure your subject stands out against the background;
Use print films, they are more forgiving;
Remember to have fun, that's what photography is all about.
Our next article will cover medium wide angle lenses.