Experimenting with a Telephoto Lens
Depth of field, or the area of acceptable focus within a photograph is influenced by three factors: the aperture of the lens, the subject to camera distance and the focal length of the lens. Our expectations for photographs are that they transparently represent the subject of the photograph. Each of the three components of depth of field offers exciting opportunities for experimentation and with challenging our expectations for a photograph.
Focal length measures the distance from the sensor or film plane to the tip of the lens, which is the distance from the point where light converges on lens to the film plane or sensor. Focal lengths also determine the angle of view of the lens. A telephoto lens reduces the angle of view, or by definition an angle of view less than 15 degrees. A wide-angle lens increases the angle of view of a scene or any lens with an angle of view greater than 55 degrees. Changes in the angle of view with both telephoto and wide-angle lens produce apparent distortions: a wide-angle lens causes objects close to the lens to appear larger than surrounding objects; a telephoto lens makes objects within the scene appear closer, or compressing space, the opposite effect that we see with a wide-angle lens. Wide-angle and telephoto lens are said to distort perspective, however this is a misconception. Perspective is influenced by your relative position or distance from a subject. The choice to use a wide angle or telephoto lens may force you to change your location will influence the perspective of the photograph.
Lumix G3 with Tokina 150-500mm: Shown here is the Tokina 150-500mm f/5.6 SD telephoto lens mounted onto a Lumix G3 Micro Four Thirds format camera. The Tokina is a manual focus telephoto lens. The lens is huge (about 5 pounds and 13 inches long) and is mounted directly on a Bogen tripod head. The Tokina is a highly regarded 3rd party lens which was manufactured between 1986-2000. The Tokina is considered an optically excellent telephoto lens.
Focal length designations vary across camera formats, and have become more complex with the introduction of new formats such as APS and Four Thirds sensors. Focal lengths for a 35mm film camera traditionally have been used to establish the baseline for focal lengths. Focal lengths for each camera format is determined by the diagonal measurement of the camera’s format. In 35mm equivalents, the diagonal for 35mm film or a “full frame” sensor is 50mm. A wide-angle lens therefore is defined as any focal length lower than 50mm, for example a 35mm, a 28mm and the popular 24mm are all considered wide-angle lens. A wide-angle lens provides a wider angle of view than a normal 50 lens. A telephoto lens is defined as any lens longer in focal length than a normal lens, and typically a telephoto lens begins with a focal length of 135mm and longer. Lens focal lengths between 50mm and135mm are considered telephoto lens, but they carry the special designation of a “portrait” lens. Telephoto lenses generate a much smaller area of focus than a normal or wide-angle lens. Wide angle and normal focal length lens appear to shrink objects in the distance relative to objects in the foreground of the photograph, where as telephoto lenses, because of the angle of view will appear to normalize the relative size of objects in a scene compared with human vision 
Lumix G3 with Tokina 150-500mm: Shown here is Tokina 150-500mm lens attached to the Lumix G3 using the LensBaby Tilt Shift Transformer adapter. The Tilt-Shift Transformer accepts accepts all Nikon F mount lens and works only with Micro Four Thirds camera and is one of the primary reason I purchased the Lumix G3. With the focal length conversion to the Micro Four Thirds format, the Tokina 150-500mm lens becomes 300-1000mm telephoto lens. As a tilt-shift lens, the Tilt-Shift Transformer also offers perspective control corrections, which are especially useful with the spacial compression issues associated with telephoto lens.
Decisions regarding focal length dramatically influence the representation of subjects within a scene. Long telephotos have traditionally only by wildlife photographers and sports photojournalist, but experiments with depth of field, compression and layering of distant objects and the distortion of scale offer great opportunities for expressive photography. Wide-angle lens have long been the preferred lens choice for landscape photographers, however long lenses, including “super” telephoto lens present opportunities for highlighting graphic relationships in nature.
DA. Donner Lake, Sierra Nevada, Ca. The Donner Lake photograph was created with the Lumix G3 and the Tokina 150-500mm lenses. The lens was set at f/8. The photograph is a composite of 24 separate photographs taken in a grid pattern from the top to the bottom of the image. The images were assembled in Adobe Photoshop using the photomerge action. By incorporating the shallow depth of field associated with telephoto lens and in particular super telephotos lens like the Tokina, varying degrees of sharpness where generated across the image to create an more dynamic visual experience. The composite of smaller images also generates larger image for print output, the final image size is approximately 25 by 60 inches.
DA, Barn and Reflection, Yuba Rice Fields, Yuba County, CA. Barn and Reflection, Yuba Rice Fields was created using the same techniques discussed in the Donner Lake image. Again the Tokina 150-500mm lens was attached to the Lumix G3 using the LensBaby Tilt-Shift Transformer. The Tilt-Shift adapter permitted a slight tilt of the camera body forward to compensate for the tendency of buildings to appear as if they are bending backwards.
 Henry Horenstein, Russell Hart, Photography, p. 79.
 David Falk, Dieter Brill, David Story, Seeing the Light, Optics in Nature, Photography, Color, Vision and Holography, p. 115.
 Henry Horenstein, Russell Hart, Photography, p. 83.