A4
Magazines, catalogues, letters, and forms can all be printed on paper that is designated as A4 size.
Dimensions
A4 measures 210 × 297 millimeters or 8.27 × 11.69 inches. In PostScript, its dimensions are rounded off to 595 × 842 points. Folded twice, an A4 sheet fits in a C6 size envelope (114 × 162 mm).
Part of the ISO 216 standard
The ISO A or ISO 216 standard refers to a group of page sizes, of which A4 is one. The German DIN 476 standard from 1922 served as the foundation for this international standard. In reality, A4 is frequently referred to as DIN A4. The JIS P 0138-61 standard for paper sizes was adopted by the Japanese.
An A4 document can be folded in half along its shortest side to become an A5. A3 paper size is equal to two A4 pages stretched out side by side. As a result, a range of paper sizes from A0 (which has a surface area of one square metre) to A10 is produced. All sizes have the same height/width ratio of 1:1.41, or the square root of 2.The dimensions always get rounded to the nearest millimetre.
Resolution needed to print an A4 size picture
To output an image properly it needs to have a certain minimum resolution. The number of pixels depends on the required output quality.
At 300 ppi (pixels per inch) an A4-sized image needs to contain 2480 × 3508 pixels. This is the required resolution for quality offset printing that will be viewed from a short distance (such as books, brochures, magazines, calendars,…). For photo books, it is also the optimum resolution but a somewhat lower pixel count (250 dpi) is fine for great-looking photographs.
At 150 ppi the image needs to be 1240 × 1754 pixels. This is the minimum resolution for newspapers or posters viewed from a fairly short distance.
A digital camera with decent image quality and a resolution of 8 megapixels or more can be used to print high-quality A4 size pictures. A somewhat lower resolution is still fine. I’ve had excellent results with my six-megapixel Nikon D70.
