Adobe Acrobat XI - Manual (Page 149)

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Creating PDFs
Last updated 1/14/2015
Default Page Size Specifies the page size to use when one is not specified in the original file. EPS files give a bounding
box size, not a page size.
Images panel options
The options in the Images panel specify compression and resampling for color, grayscale, and monochrome images.
You may want to experiment with these options to find an appropriate balance between file size and image quality.
The resolution setting for color and grayscale images should be 1.5 to 2 times the line screen ruling at which the file
will be printed. The resolution for monochrome images should be the same as the output device, but be aware that
saving a monochrome image at a resolution higher than 1500 dpi increases the file size without noticeably improving
image quality. Images that will be magnified, such as maps, may require higher resolutions.
Note: Resampling monochrome images can have unexpected viewing results, such as no image display. If this happens, turn
off resampling and convert the file again. This problem is most likely to occur with subsampling, and least likely with bicubic
downsampling.
The following table shows common types of printers and their resolution measured in dpi, their default screen ruling
measured in lines per inch (lpi), and a resampling resolution for images measured in pixels per inch (ppi). For example,
if you were printing to a 600-dpi laser printer, you would enter 170 for the resolution at which to resample images.
Downsample (Off) Reduces image resolutions that exceed the For Images Above value to the resolution of the output
device by combining pixels in a sample area of the image to make one larger pixel.
Average Downsampling To Averages the pixels in a sample area and replaces the entire area with the average pixel color
at the specified resolution.
Subsampling To Replaces an entire area with a pixel selected from that sample area, at the specified resolution. Causes
faster conversion time than downsampling, but resulting images are less smooth and continuous.
Bicubic Downsampling To Uses a weighted average, instead of a simple average (as in downsampling) to determine
pixel color. This method is slowest but produces the smoothest tonal gradations.
Compression/Image Quality Applies compression to color, grayscale, and monochrome images. For color and
grayscale images, also sets the image quality.
Anti-Alias To Gray Smooths jagged edges in monochrome images. Choose 2 bit, 4 bit, or 8 bit to specify 4, 16, or 256
levels of gray. (Anti-aliasing may cause small type or thin lines to look blurry.)
Note: Compression of text and line art is always on. To turn it off, set the appropriate Distiller parameter. For details, see
the SDK information on the Acrobat Developer Center at www.adobe.com/go/learn_acr_devcenter_en (PDF, English
only).
Policy Opens the Image Policy dialog box, where you can set processing options for Color, Grayscale, and
Monochrome images that are less than the resolutions you specify. For each type of image, enter a resolution value, and
then choose Ignore, Warn And Continue, or Cancel Job.
Printer resolution Default line screen Image resolution
300 dpi (laser printer) 60 lpi 120 ppi
600 dpi (laser printer) 85 lpi 170 ppi
1200 dpi (imagesetter) 120 lpi 240 ppi
2400 dpi (imagesetter) 150 lpi 300 ppi