Editing Image scanner (section)

=== Direct connection {{anchor|Direct physical connection to a computer}} ===
The file size of a scan can go up to about 100&nbsp;MB for a 600&nbsp;dpi, 23&nbsp;× 28&nbsp;cm (slightly larger than [[ISO 216|A4 paper]]) uncompressed [[24-bit color|24-bit]] image. Scanned files must be transferred and stored. Scanners can generate this volume of data in a matter of seconds, making a fast connection desirable.

Scanners communicate to their host computer using one of the following physical interfaces, listing roughly from slow to fast:
* [[Parallel port]]&nbsp;– Connecting through a parallel port is the slowest common transfer method. Early scanners had parallel port connections that could not transfer data faster than 70 [[kilobyte]]s/[[second]]. The primary advantage of the parallel port connection was economic and user skill level: it avoided adding an interface card to the computer.
* [[GPIB]]&nbsp;– General Purpose Interface Bus. Certain drum scanners like the Howtek D4000 featured both a SCSI and GPIB interface. The latter conforms to the IEEE-488 standard, introduced in the mid-1970s. The GPIB interface has only been used by a few scanner manufacturers, mostly serving the DOS/Windows environment. For Apple Macintosh systems, National Instruments provided a [[NuBus]] GPIB interface card.
* [[SCSI|Small Computer System Interface (SCSI)]]&nbsp;– SCSI is rarely used since the early 21st century, supported only by computers with a SCSI interface, either on a card or built-in. During the evolution of the SCSI standard, speeds increased. Widely available and easily set up USB and Firewire largely supplanted SCSI.
* [[USB|Universal Serial Bus (USB)]]&nbsp;– USB scanners can transfer data quickly. The early USB 1.1 standard could transfer data at 1.5 megabytes per second (slower than SCSI), but the later USB 2.0/3.0 standards can transfer at more than 20/60 megabytes per second in practice.
* [[IEEE 1394|FireWire]]&nbsp;– Also known as IEEE-1394, FireWire is an interface of comparable speed to USB 2.0. Possible FireWire speeds are 25, 50, and 100, 400, and 800 megabits per second, but devices may not support all speeds.
* [[Proprietary hardware|Proprietary]] interfaces&nbsp;– Bespoke interfaces were used on some early scanners that used a proprietary interface card rather than a standard interface.<!--Mustek?-->