Radio Frequency or RF, is the most common technology used in wireless speakers. The speakers use a particular unused band of the radio spectrum to transmit data wirelessly. A cordless phone works on the same principle. RF is a fairly efficient technology, flexible and affordable. It has a good range, stretching over 100 feet in certain models (and over 300 feet in some outdoor speakers).
There is a fair amount of data loss which can cause degradation of the audio signal, resulting in poor quality playback. Conflicting signals from other wireless devices in the house, such as wireless routers and cordless phones can cause interference, leading to data loss and disturbance. All in all, RF, despite its popularity, may be phased out in the next few years as newer technologies take its place.
If you bought a new mobile phone in the past 2 years, you would definitely be familiar with Bluetooth. As a wireless data transfer standard used in virtually every mobile phone, Bluetooth is ubiquitous these days. Via this technology, two Bluetooth enabled devices can be connected wirelessly within seconds. Once a connection is established, data can be transferred wirelessly at speeds of up to 3 MB/second. Technologically, Bluetooth works on the radio spectrum as well.
Instead of using a single band, however, Bluetooth chops up the data and distributes it over 79 different bands, thereby enhancing speed and reducing data loss. These bands range from 2400 MHz to 2483.5 MHz. Bluetooth has a smaller range than pure RF signals. One key issue with Bluetooth is that it isn't available in all devices.
Older phones, most audio and video players, TVs, and desktop computer aren't equipped with native Bluetooth. To use a pair of Bluetooth wireless speakers with these devices, you'll have to invest in a Bluetooth transmitter. However, if you primarily use a Bluetooth enabled device such as an iPhone or iPod Touch to listen to your music, you'll find Bluetooth wireless speakers to be a competent competitor to RF.
Only a select few speakers use Wi-Fi for transmitting data - such as the Sonos Play series of speakers. This is the same plain vanilla Wi-Fi used in your home. It is fast and efficient and works very well with digital, Wi-Fi enabled devices like computers and mobile phones. However, most audio players, TVs, etc. aren't Wi-Fi enabled. This means that a Wi-Fi wireless speaker can only play back audio from your computer or mobile phone. Obviously, this limits its functionality and is the sole reason why wireless Wi-Fi speakers haven't been accepted by the mainstream.
Most cameras, including the iPhone camera, have autofocus (AF). The camera will make a guess as to which part of the image should be in focus and adjust its focus accordingly. The built-in iOS camera app allows users to tap on something to make it focus on that part of the image — and some apps even allow users to manually set the focus.
The camera lens consists of multiple optical components. These direct and focus the light. When changing the focus of the camera, this is done by physically moving parts in the lens. Modular cameras, such as SLRs, let you switch between different lenses. And even fixed lenses, such as the one in the iPhone, let you adjust the optical part of the camera by clipping external lenses on in front of the built-in one.
The key property of a lens system is its focal length — its magnification or angle of view. A wide-angle lens has low magnification, and lets the camera see a large area. A long-focus lens, particularly a telephoto lens, has a narrow angle of view, and it shows a small fraction of what a wide-angle lens would, due to its magnification.
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