User profile for user: ProfessorP
ProfessorP Author
User level: Level 1
10 points

how do i force photos to create thumbnail previews?

Hello,


I am using the latest version of OS X El Capitan and the latest version of Photo's.


TL;DR My Photos library has around 26,000 images and it is missing about half the thumbnail and preview images so that If I click on the square I can see the image, but the square where the preview photo should be is just a blank white square.


Does Photo's fix this over time (if I leave the program open and wait long enough) on it's own?


Or do I need to force it to happen? And is there a good way force photos to create new preview and thumbnail images?


Longer story, so I recently ran out of space on my external drive, and I got a bigger one, and I discovered that my old drive was formatted in "case sensitive" (I must have inadvertently done it, not realizing the consequences). This somehow prevented me from directly copying my photo's library to my new drive (since I didn't want to continue to use a "case sensitive" formatted drive. Yes El Capitan stops the copy and prevents you from copying any part of the photos library at all since possibly some very small part of it has a case sensitive conflict.


I tried various things that didn't work to transfer the drive, including compressing the library then copying it and then decompressing it (el capitan doesn't let the decompress happen for the same case sensitive reason I think). Then someone suggested to me that I use "PowerPhotos" (http://www.fatcatsoftware.com/powerphotos/) to "Duplicate" my photo's library onto my new drive. I did this and it works and it appears that all my images copied (by using four different file counts as in Re: duplicated photos library with PowerPhotos), but when I do the duplicate it doesn't duplicate most of the thumbnail or preview images too.


Then I tried to "rebuild" my photo's library by clicking control+option when starting up Photo's but that doesn't rebuild the thumbnail previews either. Then I tried some suggestion that is in several places on the internet to delete a selected collection of files in the package contents before rebuilding Photo's... I tried that and it also didn't work. Then some where else on the internet it was suggested that I rotate my images counterclockwise and then back clockwise and that would force photos to create new preview and thumbnail images... this seemed to be working but I left it running overnight and Photos crashed this morning when I woke my computer from sleep and at that point it was about halfway done... I am running a 2012 rMBP 2.6 GHz quad core i7 with 16GB ram.


Thanks!

iMac, Mac OS X (10.7.1)

Posted on Nov 28, 2015 5:27 AM

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8 replies
User profile for user: léonie
léonie
User level: Level 10
200,645 points

Nov 28, 2015 5:49 AM in response to ProfessorP

According to Apple's knowledge base article repairing the library should recreate the thumbnails, see:

Fix missing or incorrect thumbnails in Photos - Apple Support


You can also try to select several photos at once and then use the command "Image > Rotate Counterclockwise" or simply press ⌘R. Then rotate the photos back using ⌥⌘R.

This will do a lossless edit that forces the thumbnails to be recreated.


If repairing does not recreate the thumbnails, test, if the originals can be found in your library. Perhaps the edited versions have lost the connection to the originals. Can you edit the effected photos at all?

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User profile for user: ProfessorP
ProfessorP Author
User level: Level 1
10 points

Nov 28, 2015 5:53 AM in response to léonie

Thanks!


How do I "test, if the originals can be found in your library"...


in my original post I mentioned that any blank square image that I have clicked on opens up a regular full sized image. Doesn't that indicate that the originals can be found in my library? And all the four different image count methods that I have used are consistently correct.

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User profile for user: léonie
léonie
User level: Level 10
200,645 points

Nov 28, 2015 6:00 AM in response to ProfessorP

in my original post I mentioned that any blank square image that I have clicked on opens up a regular full sized image.

The enlarged photo might be showing a preview image. But if you can export the image with "File > Export > Export ...orignal", the original image file can be accessed, also, if you can edit the photo.


Does the "rotating" method restore the thumbnails?

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User profile for user: léonie
léonie
User level: Level 10
200,645 points

Nov 28, 2015 6:31 AM in response to ProfessorP

I tried various things that didn't work to transfer the drive, including compressing the library then copying it and then decompressing it (el capitan doesn't let the decompress happen for the same case sensitive reason I think).

If a library cannot be copied as a library, you can copy it in parts, folder by folder.


Select the Photos Library in the Finder, ctrl-click it, then select "show package contents". A Finder window will open and show you the folders inside.


Create a new empty folder on the destination volume and call it "Copied Photos Library".

Then drag the items from the original library to the destination folder on the other drive, one by one. If there should be any problem with ambiguous filenames because of the lower case formatting, skip these files and reimport them later separately.


Once all parts of the library have been copied rename the enclosing folder to "Copied Photos Library.photoslibrary". After you add the extension ".photoslibrary" the icon will change to the rainbow flower icon and Photos should be able to open the library.

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User profile for user: ProfessorP
ProfessorP Author
User level: Level 1
10 points

Nov 28, 2015 1:35 PM in response to léonie

léonie wrote:


I tried various things that didn't work to transfer the drive, including compressing the library then copying it and then decompressing it (el capitan doesn't let the decompress happen for the same case sensitive reason I think).

If a library cannot be copied as a library, you can copy it in parts, folder by folder.


Select the Photos Library in the Finder, ctrl-click it, then select "show package contents". A Finder window will open and show you the folders inside.


Create a new empty folder on the destination volume and call it "Copied Photos Library".

Then drag the items from the original library to the destination folder on the other drive, one by one. If there should be any problem with ambiguous filenames because of the lower case formatting, skip these files and reimport them later separately.


Once all parts of the library have been copied rename the enclosing folder to "Copied Photos Library.photoslibrary". After you add the extension ".photoslibrary" the icon will change to the rainbow flower icon and Photos should be able to open the library.


Thanks! That worked. Turned out it was one stinking iPhoto generated thumbnail photo from 2007 that was causing the whole problem... Wish I would have tried that sooner instead of all the silly hoops that I jumped through. Also I wish when I was coping the Photo's library that OS X El Capitan would have told me the name of the offending file so I could have looked it up too... instead of just telling me that some file caused a problem and cancelling the whole copy process.

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how do i force photos to create thumbnail previews?

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