Monday, September 3, 2012

Manipulating reflections off of water for creative effects

Water can provide a beautiful backdrop for all types of images. Still water seems to convey a sense of serenity and calmness that most everyone responds to.  The look of water in a photograph can vary greatly depending on the way light hits it.  It may appear like a mirror, as in those landscape photos of snow capped mountains reflected in high alpine lakes.  Or it can look transparent, as when we photograph a swimming pool from a high angle. In today's post, I discuss how to harness a little knowledge about the way light interacts with water to control how water appears in your photographs.  

To understand how to manage reflections off of water, think about what it's like when you look through your living room window from the street.  During the daytime. you might not be able to see much of your living room at all.  The outside light is much brighter than the light inside, so if you look in the window you'll most likely see your own face reflected back at you.  On the other hand, if you wait until evening when the interior lights are turned on, you'll see the living room just fine.

The same idea applies to reflections on water.  Whether you see images reflected off the top of the water or objects beneath the surface depends on how much light is reflected off of each.  The surface of the water acts like a semi-transparent mirror, reflecting some of the light hitting it but also letting some of the light through to illuminate subjects below.  Like a pane of glass, the surface of the water only reflects light in one direction.  If light strikes the water at a 30 degree angle, it'll bounce off at a 150 degree angle, just like a billiard ball bouncing off a cushion.  In contrast, the reflective properties of objects under the water depend on what they're composed of. Typically, the bottom of a water basin or lake or stream or whatever will produce diffuse, rather than direct reflections.  This means that it'll reflect light in every direction, regardless of the angle the light comes from.  

You can use the difference in reflective properties of the surface and the bottom of a body of water to your advantage. Say you want to make an image in which a subject is reflected off the surface of the water.  In this case the subject should be brightly lit, and the bottom of the water basin should be made as dark as possible.  If I don't want the bottom of the basin to appear in a studio shot, I line it with black construction paper so that it reflects very little light.  On the other hand, if you want to be able to see through the water's surface to objects underneath it, you should position your lights so that direct reflections off the water bounce away from your camera.  

The figure below illustrates how different camera positions will yield different results.  Assume the light source on the left is flagged so that it only shines light in the directions shown.  A camera placed at position B will see direct reflections from the light off the surface of the pool.  The pool's bottom probably won't be visible.  A camera placed at positions A or C, however, will see no direct reflections off the water, but will see diffuse reflections off the bottom of the pool.

The tea candle photograph up top includes both direct reflections off the surface of the water and diffuse reflections off the bottom of the basin.  The setup for this photo was pretty straightforward.  I placed a tea candle in a baking pan lined with red construction paper and filled with about half an inch of water.  The candle and water were lit with a single flash with a pink gel bounced off a white wall behind the pan.  The camera was located at a point similar to position B in the diagram so that when the water was undisturbed the camera would see the pink flash reflected off the water's surface. To make ripples in the water, I tapped the edge of the pan just before tripping the camera shutter.  The ripples changed the angles of the water's surface and hence the direction of the light reflected off of it.  Where the angles are right, we see the pink flash reflected off the water..  For other angles, we see through the water to the red construction paper beneath it.

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