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Previews...
One of the more powerful features in Aperture is its ability to render JPEG previews of raw images that can be used in a variety of practical and powerful ways. These previews represent the original raw files and are rendered with any adjustments you’ve made to the RAW file in Aperture. You can control the size and quality of the JPEG preview depending on your needs.
Aperture can create previews for all images being imported if the “new projects automatically generate previews” box is checked in preferences. But preview generation is fairly memory intensive, and even though the previews are generated in the background during and long after import, I don't find it necessary to have full JPEG previews of all the images I import into Aperture. I wait to generate previews till after I’ve edited my work, to save time and processing power.
I choose to generate fairly large previews which I can use in other applications in the iLife and iWork suites (make sure the sharing box is checked in preview preferences).
These preview JPEGS are big enough to export and be used in high quality publications when needed. I also prefer to save my preview JPEGS at no bigger than a quality of “6”, which I find is ample for my needs and those of many publications I work with.
Within Aperture, having previews already generated is great when creating slideshows, speeding things up so there’s no waiting, as it does when editing, particularly in full screen mode. You can also drag and drop an image with a preview built, onto the Finder, Mail or other applications. The Quick Preview function doesn't need the Aperture generated previews to work, using instead the thumbnail preview embedded in most RAW files (make sure the "Use Embedded JPEG is checked), so you can still edit and rate quickly even when you don't generate previews on import.
There are many different workflows that factor into your decision to create previews. By trimming down my library by deleting images I know I will never use, I don’t waste time or space creating previews on import.
Depending on the project, I may choose to Control>Click on a project and “update previews for project”. Or, I go to my tighter edit which I place in a selects album, select them all and under “Image”, scroll down to “Update Previews”. You can also create smart albums of your three or four star selects and generate previews for those images.
For me, it makes sense to have bigger previews of my selects, than smaller ones of my entire library. But remember, the bigger the previews, the more processing power and space it takes up, so it’s not practical to have large previews unless you need to have them big.
With previews generated in a referenced library, you can have thousands of images available to you to use in practical ways, at a fraction of the size of the actual master library. And you’re never stuck with your previews at a particular size; they are easily made bigger or smaller as needed at any time.
I have to say that my reaction to previews is fairly mixed. Like you, I generate them selectively after I've done a pass of culling, rating and editing. Typically, I'll then generate previews for images above a certain rating - the ones that it seems likely I'll want to show in slideshows or use in other apps. I also appreciate them as a way to have usable copies of my better images when I'm not connected to my whole library.
However, I think that the tools we have for working with them could be greatly improved. For instance, there seems to be no way to tell if an image has a generated preview other than to try to use it in some way. The contextual menu even lists 'Update preview' when there is no preview to update.
I also have a project that I created back before I found the option to disable automatic preview creation, and it seems quite insistent that it have previews. I've tried deleting all of the previews, but it just goes ahead and automatically starts generating them again. I haven't gone poking around in the messy underbelly of my library to see if there is some hidden flag that got set somewhere yet, but that kind of behavior shouldn't be so opaque. While I agree that there are some situations where it would be handy to have a 'automatically create and keep up to date the previews in this project', it should be out in the open where I can see it and set it. For that matter, I'd like to be able to do that on an album level, so I could just put picks in select albums, or create smart albums and have previews generated and kept up to date automatically for select images based on some interesting rules.
If I've missed something or someone has a good idea for making previews less of a black box, I'd love to hear it...
"I also have a project that I created back before I found the option to disable automatic preview creation, and it seems quite insistent that it have previews. I've tried deleting all of the previews, but it just goes ahead and automatically starts generating them again."
Ahhh yes... I went though that one. Select the project that keeps creating previews, click on the gear icon at the top of the window (next to the plus sign) and make sure "Maintain previews for project" is UNchecked. Chances are that's your problem.
And I agree with you: being able to set preview flags per image or album would make my life a lot easier as well.
Steve, Thanks for this post. Could you please clarify something about previews. For purposes of this question, I am distinguishing thumbnails as smaller JPEGs and previews as larger JPEGs.
I understand that previews are used by other apps, within slideshows, and for certain exports, but are they used directly within Aperture using a managed library with RAW files for general editing workflows such as ratings, adjustments, etc?
If JPEG thumbnails are used in Browser view and RAW in Viewer and Full Screen view, are previews used at all for viewing and editing within Aperture?
Is this any different with a referenced library, or is Aperture still using the thumbnails?
Thanks in advance.
Thanks Patrick, I'd missed that option.
Thanks Patrick, I'd missed that option.
So far as I've been able to find out, Previews are only used for hi-res slideshows, and for sharing with other apps. Otherwise it's all thumbnails or full-res Versions. When you are in "Preview" mode (yellow highlight) you are viewing thumbnails, not "previews", I believe, which is confusing terminology.
I found a workaround for the slideshow issue - I defined a slideshow type called "Quick and dirty" where I selected the option of "Good" rather than "Best" previews. This appears to make use of thumbnails rather than generating larger previews. If you try to run a slideshow on a set of images that don't have previews, it has to generate them first, which means that it can take quite a while for the slideshow to actually start. My method gets around this issue, and means that the thumbnails are shown pretty much full size on my MacBook Pro 15" - if you've got a bigger screen it may not work so well.