Aperture Thumbnail and Previews Question

When is a preview used instead of a thumbnail

When you integrate with other apps via a Media Browser or drag to the desktop.

Regards

TD

Terence Devlin wrote:

When is a preview used instead of a thumbnail

When you integrate with other apps via a Media Browser or drag to the desktop.

I'd like to clarify the distinction between "Preview" and "Thumbnail". It may be just me, but I remain confused as to what a Thumbnail is in Aperture. (There is no definition in the [Aperture Glossary|http://documentation.apple.com/en/aperture/usermanual/#T].)

First to the question at hand. Previews are used for much more than the two cases TD mentions. They are used when "Quick Preview" is turned on, when the Masters are off-line, and whenever an image is rendered on screen (they appear first, while the Version is loading).

Preview maintenance is an advanced and complex subject. The [Help file|http://documentation.apple.com/en/aperture/usermanual/index.html#chapter=6 %26section=15%26hash=apple_ref:doc:uid:Aperture-UserManual-91292VWR-1036766], is, as usual, helpful.

Previews also allow one to reduce the size of one's Library. This is the preferred method (rather than the creation and importation of JPGs from one's Masters, about which we've had a couple of threads recently).

How Previews are used, however, does not answer the question at hand, which is when are Previews used and when are thumbnails used. Afaict (let me emphasize, +I don't know+ ), every image has a thumbnail, and the thumbnail is 1280 px or less on each side. Thumbnails are used in the Browser. Thumbnails are created automatically; the user has no control over Thumbnail creation or size or use.

Previews, it seems, are larger versions of Thumbnails. Their creation and use is determined by the user. They add to the functionality of Aperture by increasing performance, at the cost of storage and maintenance.

I think the answer to the OP's question, +"When is a preview used instead of thumbnail"+, is simply whenever Aperture needs to render the image on-screen in a size larger than the thumbnail.

Please forgive me for walking my way through this on-line. Previews have recently been on my mind. I welcome any clarification.

This may help you understand:

http://www.apertureexpert.com/tips/2010/5/16/a-comprehensive-look-at-thumbnails- previews-and-more-in-aper.html


More on Previews:

http://www.apertureexpert.com/tips/2010/1/20/reducing-library-sizedramatically.h tml


Pretty good info, IMHO. 😉

Excellent write-ups. Thanks CorkyO2.

Here's my question:
Thumbnails are 1280 px in their longest dimension. From the [User Manual|http://documentation.apple.com/en/aperture/usermanual/index.html#chapter =6%26section=15%26hash=apple_ref:doc:uid:Aperture-UserManual-91292VWR-1036766]:

the thumbnail image (a JPEG image that is 1280 pixels in the longest dimension).

Is there any reason not to turn off and delete all Previews if that size is sufficient for dragging images out of Aperture, using in Mail, or browsing images in Aperture while Masters are off-line?

I long ago (to decrease the sizes of my Libraries) set my Previews to "1280 x 1280" and "9". This seems to be close enough to the built-in thumbnails that I should just turn of Previews and delete. What remains to be seen is whether with that setting Aperture has been creating any Previews at all -- maybe it's just been using the thumbnails (which one cannot turn off or change).

Is there any reason not to turn off and delete all Previews if that size is sufficient for dragging images out of Aperture, using in Mail, or browsing images in Aperture while Masters are off-line?

I am not sure that you really can, as I see that if you set the following in preferences:

Deselect 'New projects automatically generate previews'

Deselect 'Use embedded JPEG from camera when possible'

Select 'Never' in the 'Share previews with iLife and iWork' drop-down

Import images and try to drag out of Aperture = unable to drag-n-drop. A look in the package shows no JPEG files in the 'Previews' folder and the Thumbnail folder only contains special files (perhaps the XML files the article refers to).

If I then go to 'Photos > Generate Thumbnails', Aperture actually creates both a thumbnail (at 360 pixels wide on longest side) and a preview that matches whatever is selected in the 'Preview Picture' options in preferences (these sizes were confirmed in Photoshop). These images reside in the 'Previews' folder.

This may be a bug, but the command 'Generate Thumbnails' is plural (even when one image is selected). So now I have a preview even though I had not specifically elected to create one with the Photo menu preview commands. It is possible that Apple just used the Thumbnail nomenclature here and they are really referring to thumbnails of Previews?

If you are comfortable in the 'Show Package Contents' command, you can create a new empty test library and see if this is the same on your machine.

In summation, this appears to mean (at least on my machine) that I cannot just use thumbnails for anything other than viewing inside of the Aperture interface. 😟

Thanks CorkyO2 -- I was just sitting down to try the exact same thing.

Will post, but expect to find the exact same thing.

The images files in the Preview folder of the Aperture library seem to be 'linked' together.

This is what I see: Create a new library, Preview & Thumbnail folders empty. Clear *new projects generate previews*. Import one image from the desktop, Preview folder still empty Thumbnail folder has subfolder and 3 data files AP.minis AP.thumbnails Ap.tinies - data files of unknown type.

Generate preview for image, Preview folder has two jpg files img_0219.jpg and thumb img0219.jpg.
Select *Delete Preview* both files gone. Select *Photos->Generate Thumbnails* both files back.

Now remove img_0219.jpg file with the finder, leave the thumbnail file. Aperture doesn't seem to care that the file was removed acts as it does if the file was removed from within Aperture.

With the thumbnail there and the preview gone you still can't drag out of Aperture.

One other thing to consider, if faces is on you'll generate a thumbnail for either faces that are in the image or if Aperture thinks there is a face in the image a thumbnail for the unknown face.

Not sure what any of this means but it sure would be nice to know just what the thumbnail is for.

Its possible that it does nothing. That is it just might be an artifact. Maybe in an earlier version of Aperture the thumbnail really served some purpose but now its not needed the preview does it all but to remove the code that deals with the thumbnail would be more trouble than just leaving it in.

FWIW, I found similar results.

Functionally, I found no difference between "Generate Thumbnails" and "Update Previews" (each is on the "Photos" menu).

Each create a JPG of the size and compression/quality specified on "Prefs→Previews". These JPGs are what gets copied when one drags-and-drops an image from Aperture to another program (inc. Finder).

If these Previews are not made at import (or later), or are deleted (via "Photos→Delete Preview") -- in short, if they do not exist -- Aperture will not transfer anything via drag-and-drop.

I can't see any worthwhile advantage from turning Previews off. To minimize the size of Previews/thumbnails, set Aperture prefs to create Previews at 1280 px. max side, with quality betw. 7 & 10. In general, set the size & quality of Previews to the minimum you need, knowing that the Preview JPG is what is used for:
- slideshows
- Quick Preview mode
- browsing and viewing (inc. zooming) when the Master is off-line
- exporting a copy of a file via drag-and-drop
- exporting a copy of a file via OS X's Media Browser (the Preview is not the file opened by other programs via "Media→Aperture" at the bottom of the sidebar in the expanded OS X "File→Open" dialog -- but the image shown in the dialog is the Preview (afaict))

What did I miss?

Hi guys,
I have an issue with thumbnails which is a little different from the subject being discussed here. However I am hoping one of you may be able to help me figuring it out. When you open a RAW file there is usually a split second between the RAW file being open (ugly photo) and the adjustment of how the picture shows on screen (nice photo). However, the thumbnails on many of my photos look as bad as the original unprocessed RAW (ie, super dark, wrong white balance…). I have set Preview quality to the max but that does not seem to affect thumbnail quality. Any idea on what to do?
Regards,
Ricardo