Digital Prints

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Mastering Digital Printing
the new and the old pixel grids are always
aligned. Scan at the next higher integer resolution,
and then downsample (resample)
slightly to the desired size (externally). For
example, scan at 600 dpi and resample to
520 dpi size later. Even divisors of 2, 4, 8
are likely better than odd divisors like 3 or
5, but any integer divisor is probably better
than other values, like 333 dpi.
■ How much resolution do I need when scanning
prints? Scanning color prints can rarely
yield more detail when scanned at more
than 300 dpi. Enlarging photo prints suffers
quality losses, at least if enlarged to much
degree. A 2x enlargement may be acceptable,
but 3x starts being poor. Enlarging film
is the much-preferred procedure.
■ How much resolution when scanning film?
When you realize that the primary purpose
of modern photo film is to be enlarged
(perhaps with a few exceptions such as Xrays),
you can see that scanning film at
3000 dpi or more is to good effect. When you need large images to print big at high-scaled
resolution, that resolution creates the pixels that effectively give the magnification necessary
to print the enlarged print. Film scanners give you those large images while retaining
very good image quality.
As to how far to go with film scanning resolution, there is no one answer for this; there
are several choices and varying opinions. The best single answer is that the scanned image
size should be appropriate for the intended purpose. There is no question that it must be
big enough to do the job, but a huge image greatly larger than the requirements can be a
rather fanciful indulgence. Except that when enlarging film, there can be subtle yet real
reasons for scanning at the film scanner’s optical maximum resolution. Or, when maximum
resolution is too ridiculously huge, an intermediate step for a smaller goal is to scan
at the next larger integer divisor of maximum. The scanner simply functions a little better
at maximum or at an integer divisor of maximum. The smaller, desired final image size
then can be resampled in a photo editor, followed by modest sharpening. Integer-divisor
scanning is a small factor, but the increased quality can often be detected. A good way to
bet is that the photo editor will do the resampling better than the scanner.
■ Are there any downsides to scanning film at highest resolution? Yes, there is a memory cost
to high-resolution scans. While image quality is usually the most important consideration
with scanning, also realize that large images consume large memory and make
computers struggle. The memory cost for an image increases with the square of the
resolution. When you multiply the scan resolution by 2, the memory cost goes up by
4 times. As memory goes up, file size goes up, too. A 35mm negative scanned at 2700
dpi in 16-bit mode is 55.5 MB in size. A 5400-dpi scan of the same negative at the
same scaling is 222.2 MB.
■ Which is better: scanning prints or film? Scanning film is better than scanning prints. Film
has more detail and contrast available; prints don’t. Film is meant to be enlarged; prints
are already enlarged. When scanning for enlargement, scan from the film if possible.
Figure 3.4 This Epson Perfection 2400
Photo scanner provides various
resolution presets including several
integer divisors (1200, 800, 600, 400,
300, 240, 200, 150, 96, 50). Custom
resolutions can also be used.