Digital Prints

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Mastering Digital Printing
file resolution. Conversely, I could shrink the image by increasing the resolution. But, again,
this only works with the Resample Image box unchecked.
If you check the Resample box, you are resampling or interpolating the pixel information in the
image to reach a desired height and width while at the same time maintaining a fixed resolution
(see Figure 3.21). You are adding or deleting pixels depending on whether you are going
up in size (upsampling) or down (downsampling). Either way, realize that you are changing all
the pixel information and, therefore, the image itself. (The Interpolation Method—Bicubic,
Bilinear, or Nearest Neighbor—determines how the new pixels are created.) This action
degrades the image to some degree, usually resulting in a loss of sharpness. I try to avoid this
whenever I can, but it’s not always
possible and a judicious amount of
re-sharpening is then employed.
An alternative to image-editor
sizing (reducing or enlarging) is
to have the printer driver or RIP,
if one is used, do it. Results can
vary so it’s best to test this
method for yourself.
File Formats, Image Compression, and More...
Image processing also requires an understanding of file formats and image compression
before a final image can be printed, transported, or stored.
File Formats
Image files are stored, shipped, saved, and opened in specific formats. Depending on which
platform you’re on (PC or Mac) and which version of Photoshop or other major image-editing
programs you have, there might be up to two dozen file formats to choose from. But for
most photographers and artists working with digital printing, there are only a few real choices.
Camera RAW
More and more digital cameras give you the option of capturing the image in the camera’s
RAW format, sometimes called by other names like NEF by Nikon. Why RAW? Instead
of the normal procedure where the image’s information is processed and adjusted behind
the scenes by the camera’s software, with RAW you get everything the image sensor captured.
RAW has it all, and usually with more bit depth (12 bits per channel).
You won’t be printing from it, but image editors like Photoshop CS will open a RAW file
with its Camera Raw import plug-in, which allows a lot of control over the image’s preprocessing
before it’s converted to one of the normal editing formats that follow.
Native Format
If you do a lot of work in Photoshop, the native format (PSD) is the one to use for preliminary
work (CDR is CorelDRAW’s native format; RIFF is Painter’s). It saves all layers,
channels, paths, etc. in the most flexible way. However, native files can get very unwieldy
Figure 3.21 With Resample Image
checked, you can change the print size
while keeping the same image
resolution, but at a cost.