Datasheet

Actual resolution needs may be somewhat flexible based on circumstances, such as paper
and equipment used, original image quality, expected results, and so forth. Be sure to read
manufacturer suggestions, and take most of the advice offered by services that offer
printing—they should know how to get the best results from their equipment.
Resizing Images
There are two methods of changing the size of an area that a group of pixels occupies: one
causes you to resample an image, actually changing the image content (using Bicubic,
Bilinear, or Nearest Neighbor interpolation), and the other changes the resolution to
redistribute pixels over a smaller or larger area without actually changing the image
content.
Redistributing pixels does nothing to actually change the content (mathematics) of
the image information that is stored; it just suggests that the content will be applied
over a different area. It is a ppi adjustment.
Resampling, on the other hand, actually changes the content of your images and
changes it permanently.
The larger the amount of resampling (the greater the percentage increase or decrease),
the more it affects the image content. The greater the redistribution, the more it affects
image size and efficiency. One of these two things, redistributing or resampling, has to
happen each time you either change the size of the whole image (using Image Size, not
Canvas Size) or change the size of a selection by stretching or transforming.
When you resample image information (upsample or downsample), changing the actual
count of pixels, Photoshop Elements has to interpret and redistribute tonal and color
information, either creating (upsampling) or removing (downsampling) pixels. It does
this through interpolation (adding image information) or decimation (removing image
information), which are really fancy names for making an educated guess. Resampling an
image to make it larger will never fill in information that is not already there, no matter
what you do and which plug-in you use. What resampling will do is estimate and average
differences between pixels to make a best guess. Details will tend to soften (upsample) or be
lost (downsample). In neither case will it actually increase the captured detail in an image.
For now, or until you are sure of what to do, set your camera to the highest resolution, and
resize images without interpolation (leave the Resample Image box in the Image Size dialog
unchecked) to 240 ppi for printing—at least until you read more and have reason to do oth-
erwise. See Chapter 11, the Appendix, and suggestions for resizing in the next section.
8 ■ chapter 1: Resolution: The Cornerstone of Image Detail
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