Taking the next steps
The root cause of most underwater photo problems is knowing how and when to use (and not use) flash – sometimes there is no right answer! I talked about white balance and using flash in Underwater Photos Parts 1 and 2 but there's no harm in saying it again – If you are getting green/blue pictures the flash is a source of white light which will cure the problem - at close range. Leaving flash set to auto mode will lead to unpredictable results as the camera decides when to use it. So take control and force it on or off yourself.
- If you are close and want a well lit, true colour picture force it on – the lightning bolt!
- If you are some distance from your subject force it off – no entry over the lightning bolt!
Knowing when to use flash will reduce the amount of backscatter you suffer, but because built-in flashes are so close to the line of the lens, you can't move far from your subject and the lighting is rather flat.
The best fix is to use an external strobe, which can light objects further away AND avoid backscatter. These are quite expensive, quite technical and can be difficult to use. It's best to understand them before jumping into the world of strobes with both feet. Some of the cheaper ones can need more expertise whilst the more expensive ones can cost considerably more than the cameras they partner. An external strobe is one of the first things ambitious divers buy for their camera, but they are not a cure if you don't understand how to use them, or how they work with your camera.
Good lighting is the key to good photographs. When you’re underwater with just a small camera and its small built in flash, light is a precious commodity and you have to make the most of it.
Any strobe or flash produces a cone of light which diverges to become wider and weaker as it gets further from the camera. So getting close to your subject makes the light available more intense – a side effect of this is that the flash doesn't have to work as hard and will recover faster and your batteries will last longer.
Doubling the distance to your subject quadruples the area the flash must light – thus it must fire four times as hard, taking four times as long to recover and cutting battery life by up to 75%. So it's best to move in as close as you can. This is another reason why a wide angle lens can be so useful, you can get still closer for the same view = less backscatter = more flash power = better battery life.
Additional wide angle lenses usually obscure the built-in flash and so really need an external flash anyway. It's probably best to think of these two items as two parts of the same upgrade, although a strobe will work separately, the lens will be very limited on its own, so it should be part two.
Strobe jargon: Manual, Automatic or TTL?
The cheapest external strobes are simple 'slaves' which fire in time with the camera flash, but don't take into account how hard it fires. As a result you must adjust the camera or flash to prevent under or over exposure. This is entirely possible, it's been done for years. However, as simpler cameras have limited controls for exposure, it may be rather hit and miss. In effect, you find a setting which works and then you will be fine whilst you stay the same distance from the same subject. You will have to adjust again if you move in or out, or your next subject is lighter or darker. This works best in a manual exposure mode where you limit the parameters which can change.
Next on the evolutionary ladder are strobes which can mimic the action of the built in flash. In old world SLR terms this is more than a simple automatic mode, but is now known by several names. These strobes copy what the camera does, but as they have greater power and are away from the centre line of the lens, can light larger areas yet allow the camera to retain control of the exposure. Usually they can be triggered with an optical fibre connection or have a sensor which can be positioned close to the built-in flash. The built-in flash can be masked to stop it firing into the scene and causing back scatter. These flashes can often be used with a variety of cameras, so can be a long term investment as you can use them when you upgrade.
The holy grail of strobe use is known as TTL control. This allows the camera's own (Through The Lens) metering to control the strobe. The automatic strobes which can accurately copy the built-in flash are offering TTL control but tend to lack the subtle control of strobes which are actually instructed how to fire by your camera. This used to be done purely by wired, cable connections, but optical systems can now offer the same accuracy. There are several advantages to optical control – the most obvious one is that there is no electrical connection which must be kept free of salt water.
Very few compact cameras offer a hot shoe for strobe connection, and even fewer compact housings cater for them, so a compact camera will usually use an optically triggered strobe. An automatic strobe which mimics the built-in flash is simplest as you can use the camera normally. The extra strobe merely adds the light the camera would if it could. External strobes are often more than four times as powerful as the built-in flashes of small compact cameras. When used with a wide angle lens which approximately doubles the angle of view, you can halve the distance to your subject – making your strobe four times as effective. This can potentially make a huge difference.
An external wide angle lens can make a big difference by cutting down the amount of water between you and your subject. Fittings on small housings vary, and surprisingly few housings (Olympus) have threaded ports which can take a screw-on lens, some others have their own fittings for their own lenses (Sealife, Sea and Sea), while most (e.g. Canon, Fuji, Panasonic) don't have any concession at all. These housings can usually be fitted with an adaptor to provide a fitting for a lens, but at extra cost. These fittings also apply to macro lenses for very close up work. Most wide angle lenses nearly double the field of view, reducing the focal length by a factor of 0.5 to 0.6. For a compact, this will make a standard (38mm film equivalent) view look like 21mm on land, BUT because of the flat glass in the housing it will act like a 28mm underwater. This is still a big improvement as the standard lens would act like a 50mm.
Jargon Alert! We talk about film equivalents as there is no other commonly used way to describe a lens' angle of view – I like degrees but nobody uses them :-(
Any extra equipment obviously has to be attached to the camera in such a way to keep it manageable, safe and useful. To add a strobe a simple tray and arm are the basic requirement. A tray is a plate to mount the camera on and attach the arm, which is a flexible support which allows the strobe to be positioned. These are a matter of personal taste; some are jointed, sectional systems which are very versatile, but somewhat complicated. Others are flexible, bendable stacks of plastic segments which are simpler, although they can't reach as far. An arm system needs to let you move the strobe out and up, away from the lens port, but also bring it down close for tight macro subjects. The jointed systems are very good at this, whereas the flex arms sometimes limit your options as they bend to a fixed radius. One day you may also want to be able remove the arm from the base plate so you can position the strobe by hand – this allows cool macro lighting and also holding the strobe way out to the side for even better reduction of back scatter.
Large arm systems can put quite a lot of strain on the small tripod mount of a compact housing, so plan to hold the arm rather than the case. If you hold the camera letting the strobe and arm just hang from it, sooner or later it will rip the tripod mount out of the bottom of the case... The camera becomes an accessory fitted to the tray, I like to use the camera's wrist strap to secure it to the tray base plate and then use something much tougher to fix the new metalwork to my BCD (Buoyancy Control Device) – if you need both hands free you'll want to be certain that your camera stays nearby!
Once the whole set of kit is assembled, it will weigh 2-4 times as much as the camera on its own and be much larger. Entering the water with these tangles of money needs some thought to stop them hitting you in the face when you jump in. If the boat won't hand it to you, the best plan is to hold it tight into your body as you enter the water. You can try to hold them over your head as you step in, but they will tend to crack you across the skull as you hit the water.
The arm, maybe pair of arms if you have two strobes or a focus light, is also a good place for storing accessory lenses... though I've always used my pockets. Your own personal preference is important, find an option which suits the way you work and keeps the whole set up manageable.
To get closer than your camera's macro mode already allows, extra lenses can be added. These will often allow you to get so close, you can touch your subject to the glass! Many people buy one before they know what their camera can do on its own. Most cameras can make a fair stab at objects less than an inch from the lens when set to wide angle but as soon as you zoom in, this can instantly step up to more than a foot! A macro lens will allow extreme close ups, but stop the camera focusing at distance and focus may become very, very finicky.
Digital cameras of all kinds like good light to focus in, so a focus light is a very beneficial add on – and one of the cheapest. A torch works fine to aid focus, but can leave hot spots on the picture. The new lights which turn off when a strobe fires are a clever solution to this and excellent for macro work. They are best fitted to the top of the housing on a simple up/down mounting, using a more flexible arm just gives you the option to point them in the wrong direction!
The Fantasea Nano Focus light is an excellent focus aid – it can make a big difference to your macro shots.
Accessory round up
In the same way that no camera can do it all alone on land there are plenty of accessories to help your underwater photography. On land these are easier to understand and there's more time to practice. Underwater time is short and they tend to be bought to achieve a quick fix rather than develop new skills.
There's no denying a good external strobe can make a huge difference, though it takes some practice. Paired with a wide angle lens you will be able to take the kind of pictures you see in diving magazines – if you practise!
These extras expand what a camera is capable of but it's up to you to exploit them. The most important part of the system is the diver behind the camera.