iPhone 4S Depth of Field (focus/defocus)

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This is a short iPhone 4S video test I did.

In optics, particularly as it relates to film and photography, depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Although a lens can precisely focus at only one distance at a time, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
In some cases, it may be desirable to have the entire image sharp, and a large DOF is appropriate. In other cases, a small DOF may be more effective, emphasizing the subject while de-emphasizing the foreground and background. In cinematography, a large DOF is often called deep focus, and a small DOF is often called shallow focus.
Affecting DOF are camera-to-subject distance, lens focal length, selected lens f-number, format size, and circle of confusion criterion. The combination of focal length, subject distance, and format size defines magnification at the film / sensor plane.
DOF is determined by subject magnification at the film / sensor plane and the selected lens aperture or f-number. For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.
When the "same picture" is taken in two different format sizes from the same distance at the same f-number with lenses that give the same angle of view, and the final images (e.g., in prints, or on a projection screen or electronic display) are the same size, the smaller format has greater DOF.
Many small-format digital SLR camera systems allow using many of the same lenses on both full-frame and "cropped format" cameras. If, for the same focal length setting, the subject distance is adjusted to provide the same field of view at the subject, at the same f-number and final-image size, the smaller format has greater DOF, as with the "same picture" comparison above. If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF. If pictures taken from the same subject distance using the same focal length, are given the same enlargement, both final images will have the same DOF. The final images will, of course, have different sizes.
Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format under the same conditions, so the cropped image has less DOF.
When focus is set to the hyperfocal distance, the DOF extends from half the hyperfocal distance to infinity, and the DOF is the largest possible for a given f-number.
The advent of digital technology in photography has provided additional means of controlling the extent of image sharpness; some methods allow extended DOF that would be impossible with traditional techniques, and some allow the DOF to be determined after the image is made. The iPhone 4S is a touchscreen slate smartphone developed by Apple Inc. It is the fifth generation of the iPhone, a device that combines the 3.5-inch (89 mm) iPod Touch with mobile phone capability. It retains the exterior design of its predecessor, the iPhone 4, but is host to a range of improved hardware specifications and software updates.
Integrated software and hardware changes support the introduction of new user interface and functions by Apple, including the voice recognizing and talking assistant called Siri, personal computer independence, cloud-sourced data (iCloud) and an improved camera system. A selection of the device's functions may be voice-controlled.
The iPhone 4S was unveiled at Apple's "Let's Talk iPhone" event on October 4, 2011 in Cupertino, California. Apple started taking pre-orders for the iPhone 4S on October 7, 2011 in seven initial countries (United States, Canada, Australia, United Kingdom, France, Germany and Japan) with the first delivery date set for October 14, 2011, and available on that same day for direct store sales in those countries. It was released in 22 more European, American and Asian countries, including Ireland, Mexico and Singapore on October 28.
It is available on 100 carriers in 70 countries overall, including AT&T, Verizon, and for the first time, also for Sprint and C Spire customers in the United States. In Japan, it is available for au (a KDDI brand) and Okinawa Cellular, for the first time. For US customers, while pre-orders for purchasers buying contracts started on October 7, 2011, unlocked (contract-free) sales started on November 11, 2011. The Associated Press said that AT&T described early iPhone 4S demand as "extraordinary".