This image was taken while on a tour of Crystal Cave in Sequoia National Park. Caves of this type form underground by water that has become weakly acidic by absorbing carbon dioxide, then dissolving away limestone or marble to create a cavity in the earth. The original rocks of the cave wall are collectively called speleogen. This type of cave is called a solution cave, due to the way it forms. After forming, the water continues dissolving minerals underground and dripping down through the cave. When the drops dry up, the calcium carbonate mineral is left behind, forming the cave features most people associate with caves. These formations are normally white, but may be tinged with orange or reddish streaks if the minerals have iron mixed in. These features that form after the cave walls, speleogen, are called speleothems. These particular kinds of speleothems are called cave draperies.
Photographically, the white calcium carbonate makes for a challenge since it can end up washed out by the flash. Having the light bright, but diffused, helps create an even lighting across the surface of the features instead of having a bright spot where the light from the flash ends up being too concentrated. A simple technique for achieving this effect is to move farther away from the features and use the telephoto zoom lens in combination with the flash, which is how this image was made. Not only will the light be softer, but cave drapery and other bright cave features to the side will reflect the light soften the shadows.
Remember, it's not just a picture, it's a story!
No comments:
Post a Comment