Apple debuted the iPhone 4 today, in a keynote given by Apple CEO Steve Jobs at the 2010 Apple Worldwide Developers Conference in San Francisco.

The new phone runs the iPhone OS Apple introduced in April, newly named iOS 4, and features a 3.5 inch Retina display at 960 x 640 pixels, with 326 pixels per inch, for sharper, smoother, more realistic looking text, images, and video. The iPhone 4 also features aluminosilicate glass, which is chemically strengthened to be 20 times stiffer and 30 times harder than plastic. The metal band surrounding the phone is five times stronger than standard steel, for structural rigidity, and also functions as both iPhone 4 antennas. Apple also added in the Apple A4 processor for added speed and performance, as well as a three-axis gyroscope for advanced motion sensing.

The iPhone's camera features also got a major update. The new phone will now have two cameras, one in the front and one in the back. The front facing camera can capture VGA-quality photos and video at up to 30 frames per second, while the rear camera can record HD (720p) video up to 30 frames per second with audio. The camera is now 5-megapixels with autofocus and a 5x digital zoom, instead of 3-megapixels, and also has an LED flash built-in. With the newly announced iMovie app, which will be coming to the app store soon for $4.99, users will be able to capture HD video directly on the iPhone 4, edit it easily with iMovie, and save it or share it in a number of different ways, all from within the phone itself.

FaceTime, a new video calling feature that was introduced, also makes use of iPhone 4's two cameras, allowing iPhone 4 users to make video calls to each other by using the forward camera, which will show the face of the user, or by switching the view to the rear camera, so a user can show someone what they are seeing. No setup is required, as the FaceTime feature has been added directly to the phone's call control screen. Now when users make a call, they will have the option of the call being a voice call or a video call. The video calling feature works with Wi-Fi only for now, but Apple is expected to be working with iPhone carriers, so 3G use of FaceTime may come as early as next year.

“iPhone 4 is the biggest leap since the original iPhone,” said Steve Jobs, Apple’s CEO. “FaceTime video calling sets a new standard for mobile communication, and our new Retina display is the highest resolution display ever in a phone, with text looking like it does on a fine printed page. We have been dreaming about both of these breakthroughs for decades.”

Battery life is also much improved over previous iPhone models, with seven hours of talk time on 3G networks, up to 10 hours of web browsing on Wi-Fi (six hours on 3G), up to 10 hours of video playback, and up to 40 hours of audio playback. iPhone 4 also features a second microphone and advanced software to suppress unwanted background noise for improved call quality, and comes with 802.11n Wi-Fi networking and quad-band HSUPA to provide 7.2Mbps downlink and 5.8Mbps uplink capability