Specifications

scanners also offer a second resolution in which the scanner’s software driver fills in fine details
lost when detailed line art or text is scanned. This second method is called interpolation and usu-
ally increases the maximum resolution of the scanner by a factor of at least 4×. Thus, a scanner
with a 1,200dpi optical resolution might have an interpolated resolution of at least 4,800dpi.
Because the interpolated resolution is software-based (instead of hardware-based), poorly-written
scanner drivers can cause poor results when using these higher resolutions. However, most scan-
ners feature excellent interpolated modes that can produce much better results when scanning
line art or text for OCR use. Although these modes also can be used for photographs, this is sel-
dom necessary because of the resolution limitations inherent in photographs (see the follow-
ing). Interpolated resolutions should not be used to scan 35mm transparencies, either.
Drawbacks of Flatbed Scanners
■ Size and bulk. Because flatbed scanners are designed to handle letter-size documents, they take
up a fairly large amount of desk space, although some newer models are hardly larger than the
8.5”×11” letter-size paper they handle as a maximum size.
■ Reflective media limitations. The least expensive flatbed scanners have no provision for trans-
parency adapters, but most mid-range to high-end models have optional adapters for 35mm
and larger negatives and slides. The scanning quality is very high when scanning 4”×5” and
larger negatives (I’ve scanned about a thousand 1900–1920 vintage glass negatives for a univer-
sity archiving project with my transparency-adapter-equipped scanner). However, because of the
limits of optical resolution, they’re not the best choice for small negatives and slides.
Slide Scanners
Slide scanners use a motorized film holder that pulls a 35mm slide or filmstrip holder past a scanning
mechanism. Even though the moving parts in the scanner are limited to the film holder, the high
optical resolution of these scanners (2,700dpi–4,000dpi are typical), the resulting precision of the
motors, and the relatively small market for transparency film make most slide scanners relatively
expensive ($700–$1600). However, a few parallel-port models are available for around $100.
Most slide scanners use SCSI interfacing and are usually limited to 35mm film, although some models
can be fitted with adapters for Advanced Picture System (APS) film holders or microscope slides. A few
slide scanners can handle media up to 4”×5”.
Although the high cost of slide scanners means they’re not for casual users, models with 2,700dpi or
higher resolution represent the best way to maximize the quality of the small 24mm×36mm (approxi-
mately 1”×1.5”) 35mm negatives or slides at a reasonable cost. They often feature advanced software
for automatically correcting color based on the characteristics of the slide or print films being scanned
and even automatic digital dust and fine-scratch removal.
Photo Scanners
This newest type of scanner is designed for users who want to scan both snapshots and 35mm trans-
parencies and who don’t want to pay a bundle to do it. This young product category has only a cou-
ple of participants at this time: HP and Artec.
HP’s PhotoSmart provides a 300dpi snapshot resolution for prints up to 5”×7” and a 2,400dpi high-
resolution scan for 35mm negatives and slides.
Note
Although the differences in scanning resolution between prints and slides/negatives seems startling, there’s a good reason
for it. Most prints don’t provide better quality if scanned at more than 300dpi because of the loss of fine details in prints.