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Focal Length
Based on a suggestion from Tess I have decided to do this month's Tips and Tricks on the use of focal length in photography. So what the heck is focal length you ask? It sounds complicated enough, but actually is very simple and even the most basic zoom camera has the ability to utilize this composition tool. In fact, focal length has a direct correlation to zoom. This is something that can be used by anyone with success.
Now, to get started...What is focal length? This term means simply how much image is the lens going to capture. Any camera with a zoom lens (do they make them without anymore?) has control over this. As you zoom in, you can get far off subjects to appear larger in the frame...everyone knew that already. As you zoom out, you can include more of the scene...again, nothing new here. So what else is there to know? Plenty.
Have you ever noticed how the relation of foreground and background changes with the zoom? I never did, until I started to read about photography. I have found out that this is a very valuable compositional tool, and one that allows the photographer a great deal of control over the way things are presented in the final picture. Before I try to explain this, allow me to illustrate it.
OK, this is confusing, but hang with me. The left half of this diagram shows a camera lens. The color coded lines correspond to the focal length. You can see numbers on the lens of you camera on most models. Ahhhh, you wondered what those numbers were. A film point and shoot I have has three settings: 35mm, 50mm, and 75mm and they are controlled by the zoom button. My Sony F828 has a continually adjustable lens at 28mm-200mm. Users of SLR cameras can purchase lenses of different lengths both fixed and zooms (able to zoom through several focal lengths). Anyway, the lower the number, the wider angle of view you are able to capture.
In the example above, a 21mm lens expands its reach at 74 degrees. Looking at the lines you can see a rough example of the field of view. As you zoom to 200mm, the field is reduced to a mere 12degrees. That changes what the camera will capture tremendously. For comparison, humans see (clearly with detail, not peripheral vision) at about 50mm, also represented in the diagram. This is the chosen focal length for many portraits because the proportions of the subject are similar to how our eyes see them. Do what????? I thought zooming in and out just changed the size of the subject.
Yes, you are changing the size of the subject but you are also changing the relationship between elements as well. Looking at the diagram on the right you can (hopefully) see this. The wider the angle, the more difference there is between fore and background. As you zoom, the lens captures elements in a more linear fashion to where the relationship stays closer between up close elements and those in the background. This is because with the wider angle, the camera will capture much more of the scenery and what is closer to the camera will become more predominant due to its proximity to the lens. As you zoom in, you are excluding what is close to the camera and only including that which is further away.
What does this mean to me, I'm confused? That's OK, its a weird concept to explain, and harder to understand. This is what it means. You can emphasize a bit of foreground by using a wide angle lens/setting and getting close to the object. It will appear huge because the lens is very close to the subject. Keep in mind that the background will be compressed causing it to appear smaller and more distant. If the background is more important and you want to change the relationship you would need to back up to another shooting location and zoom in to a higher focal length. You can still include the same foreground and background, but the background all of a sudden appears larger and more prominent in relation to the foreground which has been reduced in apparent size. This is because the subjects' distance from the camera is more closely related.
Whoever said a photograph doesn't lie was pulling a fast one on us. A photograph is the ultimate liar. By choosing a focal length, you can make a leaf appear larger than a house, or a shell appear larger than a boat on the ocean. This is a very powerful tool and one that can really set a picture apart from others of the same subjects.
An example of this technique is in a photograph I took at Hanging Rock. Rocky Way was created to emphasize the rocks in the foreground because there was not a lot of water cascading over the rocks. There needed to be something else to provide interest. I used my maximum focal length of 28mm and stood almost on top of the foreground rock which was only about 20 inches wide. Standing there looking down the stream, that rock just blended into the surroundings. By using that wide angle to capture the photograph, it became a very strong focal point with the waterfall being a secondary element. I could go back and take the same picture with the 200mm lens (if I didn't fall off the waterfall behind me that is) and you would not notice the rock near as much, and the waterfall would appear much larger.
Photo Copyright © 2006 G. Kiser
Written by Greg A. Kiser
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6/4/08 11:00 AM
Thank you so much
Nancy