Depth-of-Field and Hyperfocal Distance
Everyone knows that pictures can show elements in and out of focus. That is why most cameras require focusingeither automatically or manually. Focusing sets the only distance where a picture element appears at its sharpness. Some elements closer and further from that point can also appear sharp. The distances where this is true is called depth-of-field (DOF).
It is important to know that DOF is subjective because anything not in focus is technically not as sharp as what is in focus. The further an element is from the focus distance, the less sharp it is. If an element is far enough, it will appear out-of-focus. Far enough is in the eye of the beholder and is usually interpreted with respect to viewing size. In other words, the same image seen as a 4"x6" and as a 13"x19" will appear to have greater depth of field in the smaller print.
Even though DOF is a subjective concept, a lens' aperture and focus distance will influence the perception of depth-of-field because smaller apertures cause elements to drift out of focus slower than larger apertures. It turns out that with a given aperture, a focus distance can be calculated so that the DOF is maximized. That focus distance is called the hyperfocal distance. The hyperfocal distance depends on lens characteristics. When a particular lens is focused at the hyperfocal distance for the set aperture, elements from infinity to one third of the way before the focus point will appear in focus. This property makes the hyperfocal distance very important in landscape photography. Some point-and-shoot cameras from Pentax and Casio have a focus mode called pan-focus, which automatically sets the focus to the hyperfocal distance.
To find out the hyperfocal distances for a particular lens, you can either purchase a hyperfocal chart or use the Java hyperfocal-distance calculator below. Using it is simple, fill out the actual minimum and maximum focal length Usually printed on the front of the lens of your lens, select the minimum and maximum aperturesUsually found in the instruction manual of the camera for it, fill out or calculate the focal lens multiplierDSLR cameras come with that information in their manual and fill out the number of zoom steps you wish to see. Then, press the Hyperfocal button and the applet will display a table of hyperfocal distances according to the chosen parameters. Note that the results are subjectively based on standard human vision for a 16x20 printMost hyperfocal chart are calibrated for a 8x10 print, but people can easily print larger now.
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