Compression panel
The Compression panel contains options for minimizing the size of a PDF file. For best results in a service provider workflow, compression should be limited so that it doesn’t degrade the output quality of the file. For ease of training, this panel is now very similar to the same Compression panel in all Adobe Creative Suite 2 components.
The Compression panel controls how graphics and text are compacted when exported to a PDF file.
Options in this panel give you control over how images and other elements in the InDesign document are compressed. For each type of image, you can choose between downsampling
(which uses the average of the color values in a sample area) and subsampling (which uses the color value of the pixel in the center of a sample area). Bicubic downsampling is the slowest but most precise method, resulting in the smoothest tonal gradations.
In a print service provider workflow, output quality is the priority. If compression is applied, downsampling will be more desirable than subsampling, and lossless compression (ZIP or any of the Monochrome compression options) provides higher quality than lossy compression (JPEG).
If you must downsample, bicubic downsampling is the highest-quality option. Remember that you or your customer can simplify compression decisions just by choosing the Press Quality preset, which already uses compression settings appropriate for a print service provider workflow.
Color Bitmap Images: To compress color images, select Downsample To and specify a dpi value; InDesign only downsamples the image when its resolution exceeds 1.5 times the value you specify. For compression, we recommend choosing Automatic, and setting Quality to Maximum.
Note that JPEG 2000 compression (available when you specify Acrobat 6 compatibility) may not be supported by all RIPs and prepress applications.
Grayscale Bitmap Images: To compress grayscale images, select Downsample To and specify a dpi value; InDesign only downsamples the image when its resolution exceeds 1.5 times the value you specify. For compression, we recommend choosing Automatic, and setting Quality to
Maximum. Note that JPEG 2000 compression (available when you specify Acrobat 6 compatibility) may not be supported by all RIPs and prepress applications.
Adobe InDesign CS2 Printing Guide for Prepress Service Providers
105
