There are a number of file formats commonly used in
the graphics industry, such as TIFF, JPEG, PNG, BMP,
PSD, and GIF formats. Most of them are supported by most
image editing/viewing applications so the non-professional
user rarely considers the advantages or disadvantages
of each format.
In our standard scanning service, digitized
images are stored as JPEG with minimal quality loss.
Other image formats such as TIFF may be used upon request.
Here is a brief discussion of JPEG and TIFF,
the two most widely accepted image formats in the industry. |
 |
|
| |
JPEG |
|
The JPEG ( "Joint Photographic Experts Group", pronounced "Jay Peg")
format provides
a good size/quality trade-off. JPEG files (extension .jpg) can be
compressed up to 90%, that is, one tenth of the original
file size. This type of compression technique is often
called "lossy", because it results in a loss
of image data and thus, image quality. This quality loss
is not recovered when opening and uncompressing the
file. JPEG files are suitable for email and Web posting,
as well as for printing at non-professional quality. JPEG
compression results in a loss of quality every time the
image is compressed and saved again, so image editing should
not be done on a JPEG image. Instead, a "lossless" format
like TIFF should be used for such purposes. Many image-editing applications permit the user to choose the level
of compression, and hence the quality level, when saving
JPEG files. |
| |
TIFF |
|
The TIFF format, or Tag Image File Format (extension
.TIF), provides the best quality and is usually used for
commercial printing and professional environments. Since
TIFF files contain all data and details of the image, they
are suitable for archiving master copies of images of which
further copies or prints have to be made. The standard
version of TIFF provides no compression, so file sizes
can be very large. 24-bit RGB uncompressed image data
represents each pixel with 3 bytes, so a 6 x 4" photo
scanned at 300 dpi produces 2.16 million pixels and the
resulting TIFF file would be 6.48 million bytes in size,
or approximately 6.5 megabytes. To learn more about pixels
and dpi, click here. |
|
