Operation Manual

You can set Aperture to create and maintain previews automatically as you add or modify
versions, or you can create previews manually whenever you need them. To maintain an
efficient use of disk space and adequate display speed, you can control the size of previews,
from a preview image that has the full-size dimensions of the master down to a preview
image that is 1280 pixels in the longest dimension. You can also control the JPEG
compression quality of the previews. If your workflows do not benefit from previews, you
can configure Aperture not to create them at all.
Previews are shared with applications in iLife and iWork, and Aperture uses JPEG previews
to display images in slideshows. The result is smoother, more responsive slideshows.
However, if the previews are absent or not up to date, Aperture must render the preview
images before the slideshow begins.
You can control the creation and maintenance of preview images for an entire library, as
well as on a project-by-project or image-by-image basis.
Aperture is preset to create previews for images in the library. Previews are built as a
background activity after images are imported. If you import a large number of images,
it may take an extended time to build these previews. In that case, you may want to
temporarily stop the building of previews using the Activity window and then resume
building the previews later. Or, you can deselect the “Create previews for existing images”
checkbox and build previews on a project-by-project basis, as described in Sample
Workflows for Using Previews Effectively.
For more information about the Activity window, see Viewing Preview Generation Progress
in the Activity Window.
How Aperture Displays Images in the Viewer
When a version needs to be displayed in the Viewer, Aperture does the following:
• Aperture draws the thumbnail image (a JPEG image that is 1280 pixels in the longest
dimension).
• Aperture draws the JPEG preview, if present.
• Aperture decodes the master and applies any adjustments to it.
Once the last step is completed, the adjustment controls become available. Because
the JPEG preview is created with all the adjustments for that version, it appears onscreen
faster than the adjusted master would. The result is a sharp preview image that appears
quickly in the Viewer.
Setting Preview Preferences
Aperture provides four preference settings for controlling previews. These settings apply
to all libraries.
240 Chapter 6 Displaying Images in the Viewer