Digital photo frame
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A digital photo frame (also called a digital media frame) is a picture frame that displays digital photos without the need of a computer or printer. The introduction of digital photo frames predates tablet computers, which can serve the same purpose in some situations, however, digital photo frames are generally designed specifically for the stationary, aesthetic display of photographs and therefore usually provide a nicer-looking frame and a power system designed for continuous use.
Digital photo frames come in a variety of different shapes and sizes with a range of features. Some may even play videos as well as display photographs.
Digital photo frames' range in size from tiny keychain-sized units to large wall-mounted frames spanning several feet. The most common sizes range from 7 inches (18 cm) to 20 inches (51 cm). Some digital photo frames can only display JPEG pictures. Most digital photo frames display the photos as a slideshow and usually with an adjustable time interval. They may also be able to send photos to a printer.
Digital photo frames typically allow the display the pictures directly from a camera's memory card, and may provide internal memory storage. Some allow users to upload pictures to the frame's memory via a USB connection, or wirelessly via Bluetooth technology. Others include support for wireless (802.11) connections or use cellular technology to transfer and share files. Some frames allow photos to be shared from a frame to another.
Built-in speakers are common for playing video content with sound, and many frames also feature remote controls. Battery-operated units are also available for portable use.
Aspect ratio 
The aspect ratio of the frames can vary. Common aspect ratios include: 4:3, 3:2 and 16:9. (Sometime 16:9's are actually 15:9) Depending on the model and features, images which don't exactly fit the aspect ratio of the frame may be cropped, stretched, shrunk to fit. This could result in, respectively, images that are missing content, distorted, or which have blank space around them. This can be avoided by buying a frame with an aspect ratio that exactly matches your camera, or editing photos to the target aspect ratio before transfering them to the frame.
Security issues 
In February 2008, a number of digital photo frames, such as the Insignia brand digital frames manufactured in China, were found to be carrying a Trojan horse dubbed Mocmex on their internal data storage.