Don't know your JPEGs from your pixels from your dpi? Then read on.
JPEG - What does it stand for? Joint Photographic Experts Group. But that's neither here nor there, if you want to understand what exactly a JPEG is. A JPEG represents a particular format for capturing, storing and displaying a digital image. What's distinctive about a JPEG is that it compresses an image to about 5% of its original size; an undesirable effect of this compression though is that some detail will be lost in the process, hence the compression method being referred to as lossy. And the more often you edit a JPEG image (using image editing software such as Photoshop, for example), the more information is lost each time you make a change and resave that image.
Advantages of using JPEGs - Use up less space on your camera's compact flash card or memory stick, or your computer's hard drive.
Disadvantages - Because images are compressed, there is a reduction in image quality which is cumulative if images are continually edited and resaved. Taking photographs in JPEG format also means that there is less scope for carrying out delicate and detailed post-production work on an image as there is less information to play with in the first place.
Pixel - A contraction of the words Picture Element, pixels are the basic square building blocks which combine together on your computer screen to make up an image. Computer monitors usually have a display setting of 72 or 96 pixels per inch, so if you are using an image on a website for instance, anything higher than these figures will not improve the on-screen quality of the image and will only serve to create an unnecessarily large file. However, if you then take that tiny image and enlarge it, it will take on a "pixelated" appearance, when the individual pixels become visible.
Most computer monitors display images at 72 or 96 pixels per inch.
Notice how the appearance of the individual pixels has started to give this image a characteristically jagged appearance.
DPI - Stands for Dots Per Inch. This actually refers to the number of dots of ink that your printer can fit within one inch of an image - the more dots per inch, the better the image quality. Typically, images of 300 dpi or more are used for high-quality printing. The term dpi has, however, become a sort of shorthand term to cover the quality of both an on-screen image (more accurately described in terms of PPI or Pixels Per Inch) and a printed image, although in reality, dots and pixels are both entirely different and distinct units of measurement.
