iPhone 4

The iPhone 4 is a slate smartphone developed by Apple. It is the fourth generation of iPhone, and successor to the iPhone 3GS. It is particularly marketed for video calling, consumption of media such as books and periodicals, movies, music, and games, and for general web and e-mail access. It was announced on June 7, 2010 at the WWDC 2010 at the Moscone Center, San Francisco,and was released on June 24, 2010 in the United States, the United Kingdom, France, Germany and Japan.

The iPhone 4 runs Apple's iOS operating system, the same operating system as used on previous iPhones, the iPad, and the iPod Touch. It is primarily controlled by a user's fingertips on the multi-touch display, which is sensitive to fingertip contact.

The most noticeable difference between the iPhone 4 and its predecessors is the new design, which incorporates an uninsulatedstainless steel frame that acts as the device's antenna. The internal components of the device are situated between two panels of chemically strengthened aluminosilicate glass. It has an Apple A4 processor and 512 MB of eDRAM, twice that of its predecessor and four times that of the original iPhone. Its 3.5-inch (89 mm) LED backlit liquid crystal display with an increased 960×640 pixel resolution is marketed as the "Retina Display". Some iPhone 4 buyers have reported signal reduction when the phone is held in certain ways, especially in the left hand, as the antenna problem is in the bottom left corner of the phone's side casing. The company has offered customers a free case until September 30, 2010, or a refund within 30 days of purchase, as cases have been shown to correct this antenna problem. The latest operating system release, iOS 4.1, added functionality such as high dynamic rangephotos and the Game Center.

Design

The iPhone 4 features a redesigned structure, designed by Jonathan Ive. Most notably, the bulges of the back panel as well as the band between the front and back are gone and have been replaced with flattened surfaces. The redesign reflects the utilitarianism and uniformity of existing Apple products, such as the iPad and the iMac. The only remnant of the previous generations of iPhone is the general layout of the device; the distinctive metal structure of the iPhone 4 is more reminiscent of the 3G and 3GS. The overall dimensions of the iPhone 4 have been reduced from its predecessor. It is 4.5 inches (110 mm) high, 2.31 inches (59 mm) wide, and 0.37 inches (9.4 mm) deep, compared to the iPhone 3GS, which is 4.55 inches (116 mm) high, 2.44 inches (62 mm) wide, and 0.48 inches (12 mm) deep; making the iPhone 4 24% thinner than its predecessor, the iPhone 3GS. Steve Jobs claims that it is “the thinnest smartphone on the planet".  The reduced size of the device is primarily due to the externally placed antenna.

The internal components are situated between two panels of aluminosilicate glass, described by Apple as being "chemically strengthened to be 20 times stiffer and 30 times harder than plastic," theoretically allowing it to be more scratch resistant and durable than the previous models. The iPhone 4 is structured around a stainless steel frame which both acts as the primary structure for the device, and additionally acts as the iPhone 4's antennae. The stainless steel enclosure features three slits that divide the band into three sections; the left section of band acts as the Bluetooth, Wi-Fi, and GPS antenna, and the right and lower bands sections act as the antenna for GSM and UMTS connectivity. The act of touching the gap between the two antennas with an un-gloved hand potentially bridges these two separate antennas, leading to poor signal reception.

Display

The display on the iPhone 4 is designed by Apple and is manufactured by LG, it features an LED backlit TFT LCD capacitive touchscreen with a pixel density of 326 pixels per inch (ppi) on a 3.5 in (8.9 cm) (960×640) display, each pixel is 78 micrometres in width. The display has acontrast ratio of 800:1. The screen is marketed by Apple as the "Retina Display", based on the assertion that a display of approximately 300 ppi at a distance of 12 inches (305 mm) from one's eye is the maximum amount of detail that the human retina can process. With the iPhone expected to be used at a distance of about 12 inches from the eyes, a higher resolution would allegedly have no effect on the image's apparent quality as the maximum potential of the human eye has already been met.

This claim has been disputed. Raymond Soneira, president of DisplayMate Technologies, reported in an interview with Wired Magazine saying that the claims by Jobs' are something of an exaggeration: "It is reasonably close to being a perfect display, but Steve pushed it a little too far". Soneira continued to state that the resolution of the human retina is higher than claimed by Apple, working out to 477 ppi at 12 inches (305 mm) from the eyes.

However, Phil Plait, author of Bad Astronomy, whose career includes a collaboration with NASA regarding the camera on the Hubble Space Telescope, responded to the criticism by stating that "if you have [better than 20/20] eyesight, then at one foot away the iPhone 4’s pixels are resolved. The picture will look pixellated. If you have average eyesight, the picture will look just fine."

Camera

The iPhone 4 features an additional front-facing VGA camera, and an improved (backslide-illuminated, big physical pixel size) 5 megapixel rear-facing camera integrated with an LED flash. The rear-facing camera is capable of recording HD video in 720p at 30 frames per second. Both cameras make use of the tap to focus feature, part of iOS 4, for photo and video recording. The rear-facing camera has a 5× digital zoom.

Connectivity

In contrast to what Steve Jobs announced at WWDC 2010, recent Federal Communications Commission documentation has shown that the iPhone 4 contains a Penta-Band 3G UMTS antenna, not a Quad-Band 3G UMTS radio, as advertised by Apple. According to the FCCdocumentation filed by Apple, the radio inside the device supports; 800, 850, 900, 1900, 2100. The 800 MHz frequency, which is most commonly used in Japanese mobile phones, is not advertised as being supported by Apple.

As with many other products manufactured by Apple, the iPhone 4 also uses the 30 pin dock connector as its only external data port.

Gyroscope and accelerometer

The iPhone 4 introduces a gyroscopic sensor that enables 3-axis angular acceleration around the X, Y and Z axes, enabling precise calculation of yaw, pitch, and roll. The gyroscope complements the accelerometer, a sensor that has been present since the original iPhone, and detects the device's acceleration, shake, vibration shock, or fall by detecting linear acceleration along one of three axes (X, Y and Z). The combined data from the accelerometer and the gyroscope provides detailed and precise information about the device's 6-axis movement in space; the 3-axes of the gyroscope combined with the 3-axes of the accelerometer enable the device to recognize approximately how far, fast, and in which direction it has moved in space.

Processor and memory

The iPhone 4 is powered by the Apple A4 chip, which was designed by Intrinsity and, like all previous iPhone models, manufactured by Samsung. This system-on-a-chip is composed of a Cortex-A8 CPU integrated with a PowerVR SGX 535 GPU.  The Apple A4 is also used in the iPad where it is clocked at its rated speed of 1 GHz. The clock speed in the iPhone 4 has not been disclosed . All previous models of the iPhone have underclocked the CPU, which typically extends battery life and lowers heat dissipation.

The iPhone 4 has 512 MB of eDRAM. The additional eDRAM supports increased performance and multi-tasking.

Storage and Micro-SIM

The iPhone 4 uses a Micro-SIM card, which is positioned in an ejectable tray, located on the right side of the device. All previous models have used regular Mini-SIM cards. Depending on the operator, Micro-SIM cards may not be available for all networks globally. As a technical workaround it is possible to trim a Mini-SIM card with a knife or scissors so that it fits into the Micro-SIM tray.

As on previous models, all data is stored in flash memory, 16GB or 32GB, and not on the SIM. Unlike previous generations, the storage capacity is not printed on the back of the unit.