TL;DR It’s weirder than you think, and it’s not about preview generation per se, but rather that Aperture simply ignores previews entirely for certain photos and just uses the original/master directly.

In my case, as I reported in the stack pick bug thread, the issue seems even weirder for me.

Basically, it seems that Aperture uses the original photo for anything less than a certain resolution. I haven’t confirmed whether this is based on the preview size, but based on the camera I’ve used, the photos in my library range from older, relatively low-res photos (under 5MP), 5MP photos taken with the iPhone 4, 8MP photos taken with the iPhone 4S and a couple of point-and-shoot cameras, and 10+MP photos taken with DSLRs.

All photos at 5MP and under are available to iTunes, the iLife Media Browser, and for drag-and-drop regardless of whether previews actually exist for these photos. In fact, it seems that Aperture just hands off the “original” (nee “master”) to third-party apps, regardless of whether a preview exists or not. I’ve actually done comparisons by selecting images in various scenarios where a “preview” should be used, such as an e-mail attachment from the iLife Media Browser or simply dragging-and-dropping a photo out, and the resulting image is not only larger than my maximum Preview size, but bit-for-bit identical to the image stored in the aplibrary “Masters” folder (ironically, even an original exported using the “export” command actually differs, even in size, while the dragged-and-dropped version is identical).

The same logic seems to apply to higher-resolution photos, but only if they are shot in landscape orientation. For example, I took several 12.1MP JPEG photos from the same shoot and dragged-and-dropped them to my desktop. All of the landscape orientation shots (i.e. 4256 x 2832) were identical to the “Masters” while the portrait oriented shots (i.e. 2832 x 4256) were actual previews, using the appropriate preview settings. Note that if previews have been deleted for those particular photos, they won’t export or be available at all.

The threshold for this is somewhere between 5 and 8 MP, but I”m really not sure exactly where it is, as I don’t have any photos in between those resolutions in my library.

Note that this does not appear to be connected to preview size settings either. I currently have my previews set to “Don’t limit” but I see the same behaviour with any other setting. With “Don’t Limit” where preview images are being used the files are the same physical dimensions but are different and smaller files, making them easily distinguishable from where originals/masters are being directly used instead (in the 12.1 MP test, the landscape photos were all around 4.5-5MB where the portrait ones were all around 1MB).

So to sum it up:

- For JPEG photos of 5MP or less, Aperture doesn’t appear to use previews at all. The original/master is used for any iLife/iTunes/drag-and-drop sharing.
- For JPEG photos larger than 8MP, Aperture uses the previews for portrait orientation photos, but ignores them for landscape orientation.
- Previews are used as expected for RAW photos.

In fact, I think the real issue is that Aperture 3.3 isn’t actually creating previews for images that are under a certain size. I’m not sure if the upgrade itself would have cleaned those previews out, but the net result is that Aperture acts like previews are always available for these images, even though there are no signs of them in the “Previews” folder within aplibrary. Effectively, it acts as if a preview is always there for those images since it’s basically using the original as the preview. Generating previews for those images adds nothing new to the aplibrary bundle, and the total count of actual previews (i.e. less thumbnails) in the “Previews” folder is far less than the total number of images in my library.

If it was working properly, this approach actually makes some sense. Using the original as the preview for images under a certain size/quality or quality would save the disk space that would be required to maintain a set of otherwise redundant preview images and likely improve performance as well by simply using the originals/masters directly.

Of course, as implemented right now, it’s basically ridiculous…. Not only does it seem to ignore quality entirely, but the landscape/portrait orientation issues suggest that whatever size calculation Aperture is using is only looking at the height of the image and not the overall resolution (e.g. a 2912px high image doesn’t get a preview, regardless of width, yet a 4256px high image does).

I’m not seeing this issue at all so can’t be of much help, but I only shoot in RAW so that seems to confirm its a JPG only issue.

I can try to import some JPG files later on today to see what happens and if I experience the same issue as you all.

Paul

Yup, it definitely doesn’t affect RAW files – previews always seem to be used for those regardless of resolution, which makes perfect sense – trying to export the actual RAW as if it were a preview would be even stranger.

I actually do think there’s a certain logic to the intent behind this new “feature” but somehow the Aperture developers borked the actual implementation of it.

I should also note, however, that the issue doesn’t seem to be EXIF- or camera-related, as it affects high-resolution negative scans in my library in the same manner, most of which contain no EXIF data at all (the few that do only contain the date taken, which was added manually after import).