How Do You Plan to Connect?
VGA Connector
projectors offer a VGA (analog) connector for a computer and a composite video connector for video equipment, If your computer has a digital output, you may also want a digital connection on the projector, because it will eliminate any chance of problems, such as jittering pixels caused by poor signal synchronization.
HDMI connector
For video sources, the preferred connection choice is HDMI (assuming your video equipment has HDMI connectors), with component video a close second. Some projectors are now adding HDMI ports that support Mobile High-Definition Link (MHL), which let you project from Android devices, and in some cases, charge them, too. Many models offer Wi-Fi connectivity, usually through a (generally optional) wireless dongle that fits in a USB port that also supports projecting from a thumb drive.
