A digital photo frame (also called digital media frame) is a picture frame that displays digital photos without the need to print them or use a computer.
Features
Digital photo frames are common in 7 inch (17.8 cm) to 20 inch (50.8 cm) sizes. 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.Other may support additional mulitmedia content, such as movie clips recorded in a digital camera's movie mode, MPEG video files and/or MP3 audio. Many can display text files.
Certain frames can load pictures over the Internet from RSS feeds, photo sharing sites such as Flickr, Picasa and from e-mail. Such networked models usually support wireless (802.11) connections.
Digital photo frames typically display the pictures directly from a camera's memory card, though certain frames also provide internal memory storage. Some allow users to upload pictures to the frame's memory via a USB connection, or wirelessly via bluetooth technology. Few are able to send photos with cellular connectivity. Some frames allow photos to be shared from a frame to another.
Most 7 inch (17.8 cm) models show images at 430 x 234 pixels. With some models the width of each landscape image is stretched to achieve an aspect ratio of 16:9, which results in noticeable distortion. Built-in speakers are common for playing video content with sound, and many frames also feature remote controls.
Limitations
Because a digital photo frame's display ratio doesn't always match the original picture ratio, some pictures cannot be displayed in a satisfactory manner. For example they may be rendered too small, with black borders, or they may be automatically zoomed-in and randomly cropped. This issue can be resolved by using photo editing software to crop the pictures before transferring them to the digital frame.
Taken from : wikipedia
