Aperture: Integrating Previews into your Aperture 1.5 Workflow

What Are Previews?

Previews are JPEG images generated by Aperture that represent an original image as adjusted in Aperture. You can control the size of the previews, from full-size down to 1280 pixels in the longest dimension; and you can control the JPEG compression quality of the previews.

Aperture provides you with the ability to automatically maintain previews as you add or modify versions, or to generate the previews on-demand. Furthermore, if your workflows do not benefit from previews, then you can configure Aperture not to create them at all.

When Are Previews Used?

In Aperture’s slideshow:
In previous releases, Aperture decoded the master image and applied the adjustments on-the-fly during the slideshow. Now it uses the preview JPEGs for this purpose. The result is smoother, more responsive slideshows. However, if the previews are absent or not up to date, Aperture will render the preview images before the slideshow can begin.

Note: You can control the quality of the slideshow on a preset-by-preset basis. “Best” quality uses the JPEG previews, rendering them if necessary before the slideshow begins. “Good” quality uses the 1024 x 768 thumbnail images which are always available and do not need to be rendered.

In the Viewer:
When a version needs to be displayed in the Viewer, Aperture does the following: first it draws the thumbnail image (a 1024 x 768 JPEG); second, it draws the preview JPEG, if present, and third, it decodes the master and applies any adjustments to it. Once the third step is completed, the adjustment controls become enabled. Because the preview JPEG is created with all the adjustments for that version, it appears on screen faster than the adjusted master would. The result is a sharp preview image in the Viewer, more quickly.

For Drag-and-drop:
When a version has a preview built for it, you can drag directly from the browser to any application that accepts JPEGs, including the Finder, Final Cut Pro, Mail, and most other applications. If the version doesn’t have a preview, then drag and drop for that version is disabled. If you are dragging multiple images, but only some of them have previews, then only the versions with previews will be dragged out.

For integration with iLife and iWork:
The media browsers in the iLife and iWork applications now support browsing Aperture libraries. For each version in your library, Aperture provides two JPEGs to iLife and iWork: a 240 x 180 JPEG thumbnail that is shown in the media browser, and the preview JPEG itself (at whatever size you specified for it). If there is no preview for a version, then that image is not made available to the media browser.

In the Mac OS X Desktop & Screen Saver System Preference:
Like iPhoto libraries, Aperture libraries can be used for your screen saver and desktop picture, through the same mechanism the media browser uses.

When the master image is offline or could not be found:
In those cases, Aperture draws the thumbnail image first, and then the preview if it is present. Because the preview is of high quality, you can zoom and even use the loupe.

How to control Previews?

In the Library Upgrade dialog:
To use your library with Aperture 1.5, you must upgrade it. Aperture prompts you with the following alert:

By default, previews are created for your library. Previews are built in the background after your library is upgraded to version 1.5. Regardless of what you choose here, it is easy to switch the setting in Aperture later. You control this setting individually, for each Aperture library. For more information about turning off previews after an upgrade and selectively building them, see the section on workflows, below.

If you have a library with thousands of images, it will take many hours to build these previews. In that case, you may wish to build the previews overnight or when the computer is not going to be in use. Or, you can deselect the checkbox in the above dialog and build previews on a project-by-project basis as discussed in the section on workflows below. In Aperture 1.5.2 or later, you can prevent scheduled previews from being generated during a specific session by pressing Shift immediately after launching Aperture. The previews will be generated on the next launch.

In Aperture Preferences:
Aperture provides four controls over previews and integration as shown below. These settings apply to all libraries.

The first checkbox determines if previews will be automatically built and maintained for new projects you create in the current library (and, by extension, for new libraries). This checkbox sets the Maintain Previews for Project setting, discussed below.

The second checkbox tells Aperture whether it should create a file, in XML format, that the iLife and iWork media browser (and OS X screen saver) use to access Aperture’s library. If this checkbox is turned off, then Aperture will not make this file for any of your libraries, and the media browser and the screen saver will not be able to see your Aperture libraries. The XML file is updated whenever Aperture quits or is no longer the active application. For very large libraries, the XML file can take some time to update. In this case, if you are not sharing your previews with other applications (other than through drag-and-drop), you may decide to deselect this checkbox.

The Preview Quality slider tells Aperture what compression setting to use for the JPEG previews. The scale ranges from 0 (very high compression and relatively low quality) to 12 (very low compression and relatively high quality). The lower the quality setting, the less disk space a preview will use on disk.

The final control, a popup, controls the width and height of the previews. The default setting is “Don’t Limit”, which tells Aperture to make each preview the same size as the version. The other choices limit the preview to no larger than the specified size. Previews are never wider or taller than the version from which they are made. Aperture places asterisks (*) next to choices that match the resolution of your currently connected displays. Not all display resolutions are offered in the popup, so you may not see any asterisks here. Below is more information on how much disk space is used by previews at a variety of compression qualities and picture sizes.

Note that changing the preview quality and size preferences does not affect previews that have already been generated. If you wish to regenerate them using the new settings, you will need to use the menu items described below.

In the Project Pane’s Action menu:
Aperture provides control over automatic preview generation as shown here:

The Maintain Previews menu item controls whether Aperture automatically updates your previews when images are imported, and when versions are adjusted or created. This control can be set at the Library level, by clicking on “Library” and then clicking on the Action menu (the gear icon), or by selecting an individual project and clicking on the Action menu. If you click on the Library, then Aperture will update the setting on each project in that library. For new projects, Aperture examines the application preference described earlier (New projects automatically generate previews).

At the library level, if there is a checkmark (as seen above), then the setting is on for all projects (or for the selected project). If there is a dash (-), then some projects have their previews maintained and others don’t (a mixed state). Finally, if neither a checkmark nor a dash appears, then automatic preview maintenance is disabled for the entire library.

Changing this setting does not generate the previews. It only tells Aperture what to do the next time an image is imported, or a version is adjusted or created. To generate previews, you can use the contextual menus described below.

In menus:
You can control previews in projects by control-clicking on a project in the project pane. In addition, you can control previews on an image-by-image basis (or on a selection of images) by control-clicking on images in the browser. These are the menus that appear:

In the Project Pane, you can delete all the previews for a project, or bring them all up to date. If they are already up to date, and you select the Update Previews for Project menu item, then Aperture will alert you that no work is required. However, you can force the rebuilding of previews by holding the option key down while control-clicking. In that case, the word Update is replaced by Generate to indicate that previews will be built regardless.

In the Browser you can select one or more images and control-click to update or delete previews. You can also force the rebuilding of previews here by holding down the option key when control-clicking on those images.

Note: These commands are also available in the Images menu.

Because the slideshow cannot begin until all preview images are up to date, preview generation is done in the foreground with a cancel button to stop the operation. In all other cases, previews always created in the background. You can view the updating progress in the task list as described below.

In the Task List:
When previews are being rendered in the background, they appear in the task list as shown below:

For projects in which the Maintain Previews option is turned off, canceled previews can be rescheduled by choosing Images > Update Previews (or choose Update Previews from the shortcut menus). For projects in which the Maintain Previews option is turned on, then the previews can be rescheduled by choosing Images > Update Previews , or if the version is adjusted, or the next time you start Aperture. (Each time you start Aperture, it checks for out-of-date previews in those projects whose Maintain Previews option is turned on, and schedules them for generation. If you don't want this behavior, turn Maintain Previews off for your projects.)

Note: when rendering an individual preview, Aperture uses the current state of the application preferences for compression quality and picture size, not the setting when preview rendering began. For example, if you have the quality set to 6, then half way through rendering, you change the setting to 8, the previews that are waiting to render will be compressed at setting 8. Already rendered previews are unaffected. To update the already rendered previews to use the new settings, select them, hold down the option key and control-click. Select Generate Previews from the contextual menu.

When do Previews get rendered?

Previews get rendered on four conditions:

• When a library is upgraded to 1.5, if the “Create previews for existing images” checkbox is selected.
• When an image is imported, or version is adjusted or created, if the Maintain Previews Action menu (gear icon) is checked.
• If you select Update or Generate Previews from the contextual menu.
• Immediately before a slideshow, if the previews are not up to date, and the preset has the “Best” quality setting.

If you are encountering performance issues, you can check the Task List to if Aperture is doing work in the background. If you feel that preview processing is degrading performance, you can turn off the Maintain Previews setting for that project, and cancel the preview processing task underway. You can then generate the previews at a more convenient time.

What are some example ways to use previews effectively?

In large libraries, on a project-by-project basis

:

Since previews can take a long time to render (especially for high resolution images or heavily adjusted ones), it may be better to disable generation of previews on a large library, and instead select the projects for which you want previews. Follow these steps to control which previews are built:

• If you want to stop building previews, select Window > Show Task List
• Click on the task “Processing Previews” and click the Cancel Task button
• Close the Task List window
• Individually select the projects you want previews for, and control-click.
• Select Update Previews for Project from the contextual menu.
• Also, select Maintain Previews for Project from the Action menu (gear icon) in the Projects panel.

Old or offline projects:
Previews are displayed when masters are offline or cannot be found. This makes previews a great way of maintaining high picture quality while conserving the disk space that masters (especially RAW files) require. Here are some steps to use previews for this workflow:

• If the masters are stored inside the Aperture library, select the project, and choose File > Relocate Masters for Project.
• Select a location for these images (for example, an external hard disk)
• Click Relocate Masters
• Control-click on the project and select Update Previews
• When the previews are completed (you can tell by selecting Window > Show Task List), you can disconnect the hard disk containing the relocated masters.
• You can browse, search, and assign metadata to preview images. You can even use the loupe and zoom in to preview images, because they are high quality JPEGs.

Making previews for low-rated images:
Another way to use previews is to create a search that displays only low-rated images. You can then build previews just for those images, and take their masters offline (for example, burn them to a DVD). That way you still have good quality pictures for all of your images, without using a lot of disk space.

New or active projects:
Because previews are used by the iLife and iWork media browsers, as well as by the OS X screen saver, you can use previews as a way to use your pictures in movies, web sites, DVDs, slideshows, and podcasts. You can also download your pictures to your iPod, import them into iPhoto, or create documents with your photos with Pages. Because these images are being actively edited, here are some steps to use previews in these workflows:

• Select the project that you want to share with other applications, and click on the Action menu (gear icon). Turn on the Maintain Previews for Project menu item.
• Make sure the Aperture preference “Share previews with iLife and iWork” is selected.
• Control-click on the project and select Update Previews for Project.
• When the previews are completed, you can open up any of the iLife and iWork applications and use your Aperture images.

Smart Albums:
You can also create previews based on the results of Smart Albums, in case you want to build previews only for highly rated images or some other criteria. To do this, here are some steps:

• Make a Smart Album and configure it with a query.
• Click in the Browser and press Command-A to select all the images in the browser.
• Control-click on one of the selected images and pick Update Previews.
• When the previews are completed, you can use them for a variety of uses, including sharing with iLife and iWork, or drag-and-drop to other applications.

Note: Previews for Smart Albums are not automatically maintained—automatic maintenance is a project-level setting only. In this workflow, you need to update the previews yourself periodically, by control-clicking on the images in the album. Aperture will only build previews for the versions that have changed, so you don’t need to determine which ones to update yourself.

How can I tell which versions have previews?

There isn’t a badge indicating if a version has a preview. You can control-click on the version and select Update Preview to learn if a version’s preview is up-to-date (and Aperture will build it if it’s not up-to-date or not present). Dragging the version out of Aperture browser will provide a + symbol over the cursor if there is a preview to drag out.

Turning previews off

If your workflow does not benefit from previews, then you can turn them off completely. Here are the steps to do so.

1. Disable the "New projects automatically generate previews" preference. This will cause Aperture to not automatically generate previews for new projects that you make in the future.
2. To cause Aperture to no longer automatically generate previews for your existing projects, select the Library in the Projects pane and turn off "Maintain Previews For All Projects" the Project pane's Action menu, as previously described. You will need to do this for each of your libraries.
3. If you have already generated previews for some projects and do not want them, select the Library in the Projects pane and choose Images > Delete Previews For Library menu. This will delete all previews that have previously been generated. Again, you will need to do this for each of your libraries in which you already generated previews.

How much disk space do previews use compared to the masters?

Previews use less disk space than their associated masters, especially for high-resolution RAW files. Below are charts that show the disk space that previews take for fifty 16 megapixel 1Ds Mark II images. They were created at three compression qualities (10, 8, and 6), and at three sizes (No limit, 2560, and 1680). In the first chart, you can see how the compression setting affects the disk space use for each preview size. In the second chart, you can see how the preview’s size affects disk space use for each compression setting.