Digital Basic Page 3

For various usage and output and the lack of universal standard, there are a lot of file formats. This is why beginners found it hard to understand Digital Imaging. The most common image file formats are: BMP (Bitmap), JPEG (Joint Photographers Engineering Group), PNG (Portable Network Graphic) and TIF (Tagged Image File Format). GIF (Graphic Interface Format) is orginally for graphics, but can be used for image with very low quality.

TIFF is an image file format for MAC, BMP is for PC/WIN. JPEG is a lossy compression type of format. Lossy means that image quality will be affected by that kind of compression.

GIF is sometimes used for image, especially for its smaller size for Internet downloading, but its 256 colors limitation is not acceptable for high quality image

Digital image file is measured in pixel, e.g. 330x220 represents an image made up of 330x200=72600 pixels. To compare digital image with tradtional film image is difficult because they are based on different structures. According to a test, a frame of 135 might contains 4,000,000 pixels. This is not an accurate count. Traditional color image uses three layers of chemical dyes and digital image uses a single pixel for any point.

Although we can resize a digital image, a process called "Interpolation". It is not as versatile as it sounds. Postive interpolation means expanding and negative interpolation means reducing. No matter it is expanding or reducing, the result would not be good with high percentage of change. Such is proved by the above images.

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