by Dave Bunnell
Shooting decent photos in caves can be a daunting task even for a professional photographer who is not used to working in that environment. Caves are one of the few places to be found where darkness is total once leaving the twilight of an opening to the surface. Photography in caves is thus unique in that ALL the lighting must be supplied by the photographer. While this increases the challenge, it also offers the photographer a blank palette on which he can “paint” with light. It is remarkable how the same scene in a cave can vary with small changes in the placement of the flash(es) used to illuminate it.
In show caves like Black Chasm, there is of course lighting provided already, often in ways that would lead to desirable photos. While it may be possible to use that light for your photography, you would need a tripod to produce a sufficiently sharp photo at the exposures required, usually over a second. Most show caves won’t allow tripods, however, as they would slow up the group or produce a tripping hazard if set up on the trail. There’s also a color balance problem, although with digital cameras one can probably adjust the white balance to match the cave lighting (incandescent, fluorescent, or LED).
Most of the time, therefore, if you want good pictures in show caves or undeveloped caves, your must supply your own lighting.
Basic Principles of Cave Photography
Most modern cameras are equipped with some sort of built-in flash, or at least a hotshoe or other connection for connecting an external flash to the camera. Many cameras offer both choices.
The fundamental key to good photography in caves is simple: move the flash away from the camera. Cave photos shot with only a built-in flash, or an external one connected directly to the camera, tend to look somewhat flat and uninteresting, and often hazy. This is because very few shadows are created, and shadows help give a sense of depth to a two-dimensional image. Hazy pictures result because caves are naturally very high in humidity, and the water droplets in the air reflect light back towards the camera.
By moving the flash off the camera, more shadows are created, and fogginess is eliminated or reduced because the reflections from water drops are not in line with the camera.
If you haven’t got an external flash, the first step is to acquire one or more, and the more powerful the better for working underground. Ideally you want it to synchronize with the camera, so that it fires just as the camera shutter opens, and there are three ways you could do this:
(1) Synch Cord: A really handy accessory is a long synch cord, so that you can hold your flash out at arm’s length yet still have it firing with the camera. These can sometimes be ordered from your camera manufacturer or generic ones can be acquired from camera stores.
(2) Slave Unit: Also known as a remote sensor or a flash trigger, this is a small device that attaches to your flash which can electronically “sense” the light pulse from another flash. It can do this quickly enough that both flashes will be captured on the film or imaging device while the shutter is open. This is the method I use most often, using the small flash on my digital camera to trigger one, or more typically two or three different flash units, each aimed independently. More on slave units below.
(3) Manual firing: One of the old standby methods of cave photography is to put the camera on a long exposure or in “B” mode, and fire the flash(es) manually. Slaves may still be useful here for synching a second flash with the one which is manually fired. Because flash has such a short duration (1/1000 second or less), no tripod is needed. However, you will need one for best results if you want to manually fire several flashes in one frame. Some, but not all electronic flash units have the required manual flash switch that allows this—often it is labeled “test.”
Equipment for cave photography
Cameras
Virtually any camera can be used underground, but if you are using external flash, your flexibility will be vastly increased by having some control over the aperture, and better yet, full manual control. Most “point and shoot” film cameras don’t offer this, but more and more digital cameras seem to. Having control over the aperture allows you to get the proper exposure from your external flash, and affords control over your depth of field.
Digitals are ideal for cave photography since working with flash and environments of variable reflectivity make for lots of uncertainty, and nothing beats that immediate feedback. This is even more important if using several flashes in one image, as often it is the balance of lighting rather than just the overall exposure that may need tweaking, or the placement of a flash. With film, you wouldn’t know until you left the cave that what seemed like a small stalagmite had cast a very large shadow on to someone’s face. With digital, you would know that you need to change the position of the flash to avoid making that shadow.
Other desirable features on a cave camera include a wide angle lens, and the ability to focus manually. Digitals typically have a maximum angle from 28mm to 38mm. Wider angles (e.g., 28 mm) allow more flexibility underground, because the nature of the cave often dictates how far away you can get from your subject (there may be a wall or a gaping abyss behind you). Manual focus is important because many cameras simply won’t autofocus in the darkness of a cave. In show caves, though, the installed lighting may be enough to allow an autofocus camera to work.
The vast majority of images in this book were taken with a Nikon Coolpix 5000 (5 mp) digital camera. It has a 28 mm lens, and an adapter to allow a 19mm equivalent. Complete manual control was used every time.
Flash Units
Electronic flash units (strobes) are the bread-and-butter of cave photography. I typically carry four or more when shooting underground, ranging from very small to very powerful. The ideal flash unit is compact, powerful, has a manual fire switch, and capability to vary the output manually (i.e., to ½ power, ¼ power, etc.). Many flashes have both hotshoe and PC connections, one of which should work with your camera.
The lighting power of a flash is specified by its guide number (see sidebar), the higher the number the better. My favorite flashes, which meet all the above criteria, are the Vivitar 285, and the Sunpak 400 series, with a GN of about 80. By far the most versatile of flashes in the Sunpak 120J, which has a “bare-bulb” flash head with a reflector. Taking the reflector off gives a very broad range of illumination compared to the standard flashtube on most strobes.
To power electronic flashes, I recommend using rechargeable Nickel-metal hydride (Nimh) batteries. Get them in as high an amp-hour rating as you can find (2000 or higher in AA size). Not only are they better for the environment and less costly if you do lots of shooting, they also allow the strobes to recharge much more quickly than do alkaline cells.
Flashbulbs are not made any more, but are very useful for cave photography because of their high power and ability to spread light out over a wide area. They can also be used underwater, as in the various shots of the lakes in this book. Bulbs and the units to fire them can still be readily obtained on ebay or www.flashbulbs.com. Unlike electronic flash, bulbs can only be used once.
Slave units
As mentioned above, slave units can be attached to external flash units and triggered by a small flash on the camera. These units range from about $20 to $80. Many of the cheaper units are rather insensitive, and will only work if fairly close to, and in direct line of sight of, the trigger flash. Better units can respond to even reflected flash, and at great distances. The Wein Ultra-slave is rated by the manufacturer to respond to a flash 1500 feet away! Two highly sensitive slaves are manufactured specifically for cave photography: The Firefly Slave and the Gibson Slave.
Protecting your gear
If you only intend to shoot in show caves, gear protection involves little more than it does on the surface, such as a padded camera case. But shooting in undeveloped caves requires much more. They may be muddy and wet (as in the lower reaches of Black Chasm), and gear may have to be dragged through crawlways and pushed through small openings. I typically use waterproof plastic containers for my gear, such as the boxes made by Pelican and Otter. Less expensive options are Tupperware or other food containers. A bit of duct tape or stout rubber bands help ensure that the lid remains attached as they bounce around in a cave pack.
Putting it all together
Lighting principles
While we want some shadowing to provide a sense of depth, we don’t want large, harsh shadows. A classic way to shoot a scene with two flashes is to have each at about 45-degrees to the camera. Each produces shadows, but harsh shadows tend to be canceled out. Often one uses a powerful main or “key” flash, and a second, weaker one to reduce the harshness of the shadows. Backlighting (aiming the flash directly towards the camera) produces very dramatic effects, bringing out wall features such as scallops quite well. Many cave formations are translucent, and backlighting can be used to emphasize this, as in the photos of the bacon on pages 38.
Flash placed underwater (pages x,y,z) can emphasize the blue-green nature of cave water. Otherwise, water often acts as a “light sponge,” because it often absorbs rather than reflects light, and can look very dark in relation to the rest of the scene.
Show Cave:
Unless you are photographing a particularly attractive cave formation, usually as a close-up, most cave photos tend to be more interesting with people in them. They give a sense of scale to the image, and if in motion, a sense of something happening in the image. If on a tour, typically I use one external flash with a synch cord that I can hold, and if someone is on the tour with me, they can hold a second external flash with a slave. Good pictures can be taken fairly quickly this way, but keep in mind that other people’s flashes will also trigger your slave.
Undeveloped caves
Without the constraints of a tour, you have much more flexibility when shooting in undeveloped caves. Indeed, the chief constraints are your equipment, the patience of those assisting you, and the need to protect the cave. The importance of the latter cannot be over emphasized. When shooting in delicate areas, utmost care must be taken not to damage the cave. Stepping on a bed of crystals or putting a muddy boot onto clean flowstone are never justified, no matter how important it is to get the flash in “just the right spot.” But there are many tricks that can be used, such as putting the flash on a monopod and holding it where you need it.
The ideal photo team has at least four people: one to act as a model, and two to man the flash units. The latter can help you compose your scene by shining their lights from the flash position. With fewer people, you can use tricks such as setting the extra flashes on rocks or ledges, or on tripods.
Remember to reward those who help you with copies of your best photos, since they have put in their time for YOUR photos.
Further reading
There is far too much to say about cave photography than can be said here. But there are two excellent books on the subject available through the National Speleological Society’s bookstore (www.caves.org). These are Images Below, by Chris Howes, and On Caves and Camera, published by the Society with contributions from many authors, including several chapters written by me.
Source: http://www.goodearthgraphics.com/showcave/photo.html