For those of us who use a compact digital camera for "casual" purposes, we've had the experience of setting up our shot, getting our subjects just where we want them, and then presto; the resulting image shows the top of the head or an arm missing from the scene.
What occurs in these instances is a frustrating phenomenon known as "parallax error". Stated simply, it is the result of the camera having one lens through which the camera focuses and records images and another lens through which the photographer views the scene to be shot. The two views are not identical and thus, the image that results is not always as we envisioned it through the viewfinder. This error is most pronounced when shooting at close range; such as in most "portrait" type shots.
Even those of us who are amateurs can avoid "parallax error" by one of just a few methods.
• Use the correction marks. Many digital cameras provide lines that can be seen through the viewfinder which approximate the border of the image being taken to visualize what the lens is truly seeing. The photographer then needs to adjust the shot as necessary. Reading the owners manual will reveal whether a given camera has this feature.
• Use the LCD to frame the shot. The LCD screen better represents the image that the picture-taking lens is seeing. There are limitations however with this method. First, the LCD screen is sometimes difficult to view in bright, outdoor light making it difficult to use in such situations. Secondly, the LCD screen on many digital cameras displays only 85% of what the lens sees which can result in more of a scene being captured versus less The final drawback is simply the extra energy required to operate the LCD. An electronic viewfinder is another option. An EVF takes the image captured by the lens and electronically transfers it onto a display screen.
• Consider the purchase of a digital camera with a TTL mechanism. The parallax error occurs with any TLR (twin lens) camera but not those with a TTL mechanism (through-the-lens). With TTL, the photographer views a scene through the same lens that records the image and is thus able to frame a scene accurately. SLR (single lens reflex) cameras use TTL. These cameras however, are considerably more expensive, bulky and complicated than a compact or traditional point and shoot type camera although for an avid amateur the additional control they offer to the photographer is a tremendous asset.
For the average consumer, a compact or point-and-shoot camera is the product of choice due to their portability and ease of use. Even with these more basic models, use of the correction marks or the LCD screen to frame shots taken at close range can help to significantly reduce any parallax error. For others who may want more creative control and don't mind a larger and more complicated camera, an SLR camera can eliminate parallax error altogether.
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