Thursday, January 7, 2010

Create A Sense Of Depth In Your Pictures - Part 2

Part 1 in this series, explained the importance of “depth of field” in conveying a sense of three dimensions in a photograph.  The next three tips are useful when taking pictures with great depth of field – like landscapes.  In these images, using shallow depth of field is not an option, because of the necessity to have as much of the scene in focus as possible.

So how does our eye/brain interpret distance in scenes with extreme depth of field?

The technique suggested in this tip is based on the visual phenomena called “convergence of lines”.  Lines that our eye/brain recognize as being parallel in reality, but visually merge at a vanishing point within a picture, provide us with the critical cue that distance is present, and that the scene does not exist on a single flat plane.

Pictured above is the classic “train tracks disappearing into the horizon” image.  We don’t need to be engineers to understand that, in order for a train track to work, the distance between the rails MUST remain constant.  Any time lines appear to defy the laws of physics by converging, as in the picture above, our eye/brain interprets this clue as distance in the picture.  As a result, the picture above not only exhibits the 2D elements of height and width (defined by the borders of the picture), but also the missing third dimensional aspect of depth as provided by the converging lines of the train track.

Similar to the train tracks, the convergence of the sides of the highway (above) is perceived as depth and conveys a sense of great distance to Mt. Saint Helens in the background.  For the viewer, it’s impossible to resist the sense of the third dimension and to be brought visually into the picture.

The convergence of lines in the picture above is subtler, but remains a very powerful cue for our eye/brain to perceive depth in the picture.  The width of each step decreases as the eye travels up the stairway.  Since this “can’t” be the reality, we interpret each smaller width as being farther away.  In total, the stairway’s converging lines ad the element of three dimensions to the picture.

As you may have noticed, using converging lines as a photographic tool to instill a 3rd dimension also provides an added bonus.  Our eyes will naturally follow converging lines into the scene.  It’s irresistible.  Managing converging lines will add the 3rd dimension and draw your viewer into the picture.  How about that?  A twofer.

In Part 3 of this series another of nature's visual cues, atmospheric perspective, will be discussed to understand its role in lending a sense of depth in photography.

Monday, January 4, 2010

Creating A Sense Of Depth In Your Pictures - Part 1

The borders of our pictures automatically provide viewers with two dimensions – height and width. Creating a 3-dimensional world on a flat computer monitor or a photographic print is a bigger challenge for the beginning photographer. But it is a critical skill that photographers master to add realism and draw viewers into their pictures. To add the sense of depth to pictures, we’ll first consider how our eye/brain combination senses three dimensions in the real world. By applying these visual cues to our photography, we can instill the illusion of three dimensions in our pictures.

This series of blog entries will present several methods of introducing the 3rd dimension into our photographs.

What Our Eye/Brain Sees

One of the most important cues our eye/brain seeks out, in its search for an understanding of any scene, concerns focus. In photography we call the phenomenon “depth of field.” Our brain understands that when there are multiple objects in a scene, and they are all equally sharp, then they are probably located on or very close to the same plane.

© 2008, Hub

Above is a simple flower picture. The main subject is obviously the large yellow dahlia. Notice that all the smaller flowers (pansies) surrounding the dahlia also appear sharp. To our mind, logic dictates that all of these flowers must be very close together (from front to back). Because everything is in focus at the same time, there is no obvious visual cue for our mind to place any degree of the third dimension to this picture. As a result, it looks flat and two-dimensional.

Experiencing the Third Dimension

Contrast the first picture with this version of the same scene below.

© 2008, Hub

In this image the dahlia remains sharp, but the pansies are soft and out of focus. Our eye/brain thinks, “Ah, there MUST be distance (or depth) in this picture because there is a visual difference in the sharpness of the elements that make up the image.” We immediately attribute this difference in focus to be the result of their spatial locations in the real world, and we mentally experience the third dimension of depth.

Controlling Depth of Field

We create this 3D illusion when we take the picture. We visualize the final print BEFORE pressing the shutter release button. And, when using a camera with aperture controls, we intentionally select an f/stop that will render this "selective focus" effect.

Large aperture openings (smaller f/stop numbers) create increasingly shallower depth of field (more and more of the scene in front of and behind our focused subject is out of focus or blurred) and infuse that important sensation of three dimensions into our photographs.

Shown below are a series of photographs taken of the same subject to illustrate the impact of aperture size to the amount of the total image that is in focus.  The camera's focus point in these pictures was the foreground bottle.  Notice that as the f/stop number increases (and the aperture opening size decreases), the bottle in the background becomes increasingly sharper.  Also notice how depth is emphasized by the out-of-focus background image, AND how your eye is drawn FIRST, like a magnet, to the sharpest object in each picture.

(All pictures in this series were shot with a DSLR in Aperture Priority Mode.  As the f/stop was manually changed to visually depict the effect of f/stop change on Depth of Field, the camera automatically selected the new, appropriate shutter speed.)

By learning to control depth of field, we – as photographers – infuse the third dimension into our imagery. Since our eyes are automatically drawn FIRST to objects that are in focus, we are also intentionally directing our viewers' eyes to the subject of our photograph.

But Wait a Minute...

I hear you asking, “Then what about landscape photographs were everything is in focus from foreground to background. How do I inject three dimensions into this 'totally in focus' picture?" That will be our next tip for creating the illusion of 3 dimensions.