Introduction
 Digital photography has drastically changed the way the world takes photographs. From the pro to the individual taking family snapshots, digital imaging is now the most popular option. Film still has certain advantages over digital but for most people the advantages of digital outweigh the disadvantages. Very few new film cameras are being produced, but every month manufacturers release new and improved digital cameras and accessories. This is a very good indication where the world of photography is heading.
In the world of underwater photography, digital imaging has changed the landscape. The biggest advantage is seeing your photos before you even surface. This way you see your mistakes, make corrections and re-shoot. When shooting film, many a photographer would return from a trip, process their film, and be disappointed. A wrong setting or some other uncorrected problem could have the photographer return from a trip without images. Also, the price and size of many Digi-cam camera housings encourages many divers to descend with a camera for the first time.
Types of Digital Cameras and Using Them Underwater
 For our purposes, we need to divide digital cameras into two groups: Single lens reflex (SLR) and digi-cams. SLRs look like and are the size of SLR film cameras. They have the ability to change lenses, have
advanced features and are usually faster then most digi-cams. These cameras require a good working knowledge of photography; they are also large and expensive. Digi-cams appear more like film point & shoot cameras. They have built in lenses, can be very small in size and may have limited or no advanced features. These cameras are much easier to use but have limitations.
 Digital cameras in both categories are getting better while prices keep getting lower. Many camera manufactures now produce economical housings for many of their digi-cam models. Third party companies produce housing for a variety of digital cameras in both categories that vary in price from $150 to $5000. A low price digi-cam camera in an economical housing is great for underwater snapshots. It can also take great photos if used within the gears limitations. A low-end gear configuration is also good for someone starting out in underwater photography. As you grow in both your land and underwater photo skills you will want to upgrade your equipment.
 One of the problems with using digital cameras underwater is that the controls are accessed mechanically. So whenever you want to upgrade to a new camera, the smallest change in size or control button position means a new housing must be purchased. This might change in the near future. Some companies are working on a new housing that controls a digi-cam electronically through a connection to the camera's USB port. This will allow the same housing to be used for many different cameras. Since the controls are electronic, the housing control buttons don't need to penetrate the housing wall with an o-ring seal-greatly decreasing the chance of a flood.
Keeping Color Natural: White Balance and Filters
Using available light and letting the subject go blue or green could be a nice effect.
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Photography is the art of creating images with light. The fact the image is captured on a chip instead of on a piece of film does not really matter. Most of the rules and concepts remain the same. This is especially true underwater. There are certain concepts of underwater photography that remain the same with film or digital. Depending on the subjects and environment you are shooting in, this will effect your gear selection.
As you go deeper underwater you start to lose color. Both film and digital chips are more sensitive to this than your eyes.
In cold northern and fresh water, your images will go very green. In warm water the color will go blue. In 60' or shallower water you can use a filter to bring back some of the color. With digital cameras, you can change the white balance of your chip. In effect, this is putting an electronic filter on your camera. Some cameras have underwater white balance presets. The setting is for blue water only. To use this feature, you would go to white balance in the menu and pick the 'underwater' icon-usually represented as a fish.
For cameras that don't have an underwater preset you can do a custom white balance. Use a white slate and follow the directions on your camera to do a custom light balance just like you would do on land. For best results, do the white balance at the same depth you are planning on shooting at.
 An alternative to white balance is to use a filter made to correct for underwater color. Sony (www.sony.com), Fantasea (www.fantasea.com) and Ikelite (www.ikelite.com) make warm water filters for many of their housings. Manufacturers of underwater video housings such as Equinox (www.dive-equinox.com) and Amphipico (www.amphibico.com) make both cold and warm water filters in a variety of sizes. These filters could be adapted for still cameras as well although it might not be easy to fit the filter to the camera or housing.
 Whenever you are using a filter or underwater white balance, it is important that all flash or other artificial light is turned off. These filters are for available light only. For some subjects like shipwrecks, just shooting available light and letting the color go green or blue could be a nice effect.
Artificial Light: Strobes
 The best way to correct for the lack of natural color underwater is to bring an artificial light source close enough to your subject to bring the color back. For still photography the most common way to do this is to use flash. Not only does electronic flash have the same color light as the sun, it also freezes action. The small built–in flash on most digi-cam cameras have limited use underwater. The main problem with the built–in flash is that it is usually positioned directly over the lens. No matter how clear the water looks, there are always particles in the water.
When the flash is over the lens, the angle of the light will illuminate all the particles and they will bounce back right into the lens. This creates a white spot effect in your images called "backscatter".
 If you are very close, the water is really clear and you do not stir up the bottom, you might get a good photo with the built in flash. A diffuser in front of the flash will help a little. The best thing to do is to use an off camera flash.  You will also need a tray and arm to position and hold the flash to your camera and some way to fire the flash. Underwater strobes (electronic flash) come in prices ranging from $175 to $1000 or more. Remember photography is the art of creating an image with light so buy the best strobe you can afford. Companies such as, Sea & Sea (www.seaandsea.com), Sealife (www.sealife-cameras.com), Bonica, (www.bonicadive.com) and Ikelite manufacture strobes for a variety of budgets.
 When buying a strobe there are many features that need to be considered. First of all, is the flash digital compatible? Many digital cameras use a pre-flash to get exposure information. Older strobes will not work with these cameras. Most digital SLR's do not use a pre-flash when connected by a sync cord. Older strobes should work but only in manual exposure mode. Most digi-cams will need a pre-flash compatible strobe.
Sync Cords and Optical Slave Triggers
 Next, how do you fire the strobe? All SLR camera housings as well as some advanced digi-cam housings allow use of sync cords. A sync cord is a hard wire device that connects the flash to the camera. Usually, there is a wire inside the housing. This wire attaches to the cameras hot shoe on one end. The other end is attached to a bulkhead on the housing. The bulkhead sticks outside the housing on the other side allowing a waterproof seal attachment for a sync cord. The other end of the sync has a waterproof seal that attaches on to the strobe.
This can start to get very confusing. Most housing companies use a Nikonos style 5-pin sync connection. Ikelite has a connection that is only for Ikelite housing. Also, every strobe manufacturer uses a different connection on their strobe. So if you are using an Ikelite housing with an Ikelite strobe, you need a sync cord that has an Ikelite connection on both sides. If you are using a Sea & Sea housing with a Sea & Sea strobe, you can get a Sea & Sea Sync cord that will have a Sea & Sea strobe connector on one end and a Nikonos connector on the other for the housing.
 Ikelite makes many different sync cords. So if you are using an Ikelite strobe with an Aquatica (www.aquatica.ca) housing, you can get an Ikelite sync cord that has the Ikelite connector on one side for the strobe and the Nikonos connector on the other side for the housing. Again before buying the camera, housing and strobe it is best to do your research on what will work.
Sometimes this is hard info to get. For example, Olympus (www.olympusamerica.com) makes a very nice budget minded housing for their cameras. Their housings for some Olympus advanced digi-cams do have a bulkhead. You need to do a lot of research to find out that the bulkhead will only work with an Olympus strobe housing for their land strobes.
This is very limiting for many photographers and with this info the photographer might decide to buy the more expensive Ikelite housing for the same camera.
If your camera and strobe combination allow TTL exposure control you have to make sure you have the correct sync cord so the camera and strobe can communicate to each other.
 Many digi-cams do not have hot shoes so there is no place to make a connection with a sync cord. For these cameras, you need an optical slave trigger to fire the strobe. The way this works is , when the built-in flash fires, the light triggers the off camera flash. Some strobes have built-in slaves while others require a separate slave. Again, it is important to make sure the strobe and the slave are pre-flash compatible if the camera uses a pre-flash. To make this light trigger more efficient, some strobes use a fiber optic cable. This cable attaches to the housing over the built-in flash and connects on the other end to the slave. The light travels up the cable and triggers the off-camera flash. Another advantage of this cable is that it covers the built-in flash and helps prevent "backscatter". In selecting a strobe, it is important to see if the strobe has or allows a slave trigger to be used. Some strobes have a slave trigger only and do not allow use of a sync cord. This might be okay for your digi-cam but remember, if and when you upgrade to an SLR you will need a new strobe. When using this kind of connection, most of the time you will not have TTL exposure control. Automatic and manual exposure control will need to be used.
TTL, Manual Exposure and Other Strobe Features
The shutter speed of the camera was set to underexpose the background to make it black while the f /stop was set for proper exposure on the shark.
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You also need to consider exposure control. Manual control requires the most skill but gives you the most control.
When you shoot underwater, you want to use the shutter speed to control the lightness or darkness of the background. Then use the aperture to get proper exposure on the main subject. Of course this requires that the camera allows you to control the shutter speed and aperture (f/stop). Some strobes have a dial so you can dial the intensity of the light higher or lower. This can be a very useful feature on a strobe. For digi-cams that have "Auto" only, proper exposure can be dialed in on the strobe. Ikelite makes a manual controller. This is a slave that allows you to dial the strobe power up or down. This is an additional piece of equipment. Some other high-end strobes by Sea & Sea as well as the more economical strobes by Bonica and Sealife have a built-in controller.
Automatic exposure is done two ways. Auto strobes have a sensor mounted in front of the strobe. This sensor determines when the appropriate amount of light has been provided by the strobe. The sensor picks up light reflected by the subject area and extinguishes strobe output when it calculates a correct exposure for a certain f/stop. Sea & Sea as well as Bonica have strobes that work this way. These strobes do not talk to the camera so they will work with many different cameras.
Through-The-Lens (TTL) exposure control, the sensor is inside the camera. This sensor determines when the appropriate amount of light has been provided by the strobe. The sensor picks up light reflected by the subject area and extinguishes strobe output when it calculates a correct exposure. Since the sensor is placed where the light enters the camera, it is more accurate. It is also more complicated since the camera and strobe have to talk to each other.
When a camera is in housing, the electronics in that housing have to be compatible with that system. Ikelite does make housings that work TTL when using their digital TTL strobes, including the DS-50 and DS-125.
Not all their housings are TTL. Other companies of digital SLR housings also make housings for land strobes. So if you use a Nikon D70 camera in a housing with a Nikon SB-800 strobe in a housing, they will talk to each other and the TTL will work.
The shutter speed was set to properly expose the background to make it a pleasing blue while the f/stop was set for proper exposure for the two strobes to light the diver and the inside of the wreck. The divers strong HID light is overexposed but adds interest to the photo.
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Another consideration when buying a strobe is the angle the light will cover. If you are shooting with wide-angle lenses, you need a strobe that will cover the whole area. Some photographers like to use two strobes for this purpose and to create main to fill flash ratios, to fill in the shadows. Also, some high-end strobes have a built-in aiming light. This is a small, continuous light that helps you point the light correctly. Since everything underwater looks 25% closer, many new photographers point the strobe in front of the subject instead of at it. Built–in aiming lights help prevents this from happening. It also makes your strobe into a dive light for night dives.
Strobe Arms
 Make sure you have a strobe arm that is flexible enough to easily position the strobe where you want it. The best arms are two or more sections attached to each other with a ball clamp. These are called ball joint arms. Another good arm type is made of small sections attached to each other that can individually be moved. This is called a flexible arm.
For wide-angle photography, you will want long 16 to 20" arms in order to move the lights far to the side to avoid "backscatter"; it is best to use 2 lights for even lighting. The same arms can be used for macro photography, but 8 to 12" arms are adequate. Two strobes can create some interesting lighting effects but one strobe is adequate for macro.
Continuous Light
In overhead environments such as caves, continuous lighting is easier and can be safer. Remember that photography adds more task loading and should only be done in an environment that you already feel comfortable in. Safety always comes first.
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Some photographers like to use continuous video lights instead of flash. When using these lights you have less control in balancing out the ratio of available-to-artificial light, but they can be easier to use. Cameras can be set on automatic & you can just shoot. Continuous light is also good in overhead environments such as inside shipwrecks and caves. When using continuous light, the photographer does not have the extra task load of handling a separate light for vision and a strobe for imaging. |
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