3.3

Table Of Contents
Chapter 5 Displaying Photos in the Viewer 115
Working with Preview Images
An Overview of Preview Images
Aperture allows you to create and use JPEG previews of versions in the library. Preview images
improve the display of photos in Aperture and allow you to easily use your photos in other
applications. These preview images are used to speed up the display of photos in the Viewer,
in the Browser, and in Full Screen view. Previews are JPEG images generated by Aperture that
represent the original photo with any applied adjustments.
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 ecient
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 original 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 workows do not benet from previews, you can congure Aperture not to
create them at all.
Previews are shared with applications in iLife and iWork, and Aperture uses JPEG previews to
display photos 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 photo-by-photo basis.
Aperture is preset to create previews for photos in the library. Previews are built as a background
activity after photos are imported. If you import a large number of photos, 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 Workows for Using Previews Eectively on
page 120 .
For more information about the Activity window, see Suppressing Preview Generation on
page 118 .
How Aperture Displays Photos 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 original 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 original 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.
To open Aperture preferences
m Choose Aperture > Preferences, then click Previews.