While participating in a recent thread about Adobe Bridge speed in generating thumbnails and previews I did some testing and came up with a mystery I can't solve.
On my Photoshop CC 2014 installation, the Bridge preference to "Keep 100% previews in cache" appears to do nothing. Actually, it appears to do nothing most of the time, but it does something some of the time and at a randomness I can't explain.
In the root folder of the Bridge cache there are 4 subfolders named 256, 1024, data, and full. The "data" folder contains the actual database. I understand that, and see no issue there.
The "256" and "1024" folders contain jpeg thumbnails for the cached images, in sizes indicated by the folder name. Actually, the "256" folder contains small thumbs that are always 256 pixels on the long edge. The "1024" folder contains larger thumbs that are either 1024 pixels on the long edge OR equal to the size of your monitor's long edge. Which size depends on the "Generate Monitor-Size Previews" option in the Bridge Advanced Preferences. I understand that, and think it's been that way for a long time.
The mystery I have involves the "full" folder. On my system I have a root folder for images. It has almost 30,000 files in 400 sub-folders. In the Bridge Cache "256" and "1024" folders I see a clear one-to-one relationshop between the cache thumbs and the image files.
But in my Bridge cache "full" folder, I have only 10 sub-folders containing about 15 jpegs. Those jpegs are, in fact, full sized versions of their source image. But I can make no sense of why those 15 are there and thousands of others are not. In recent testing I've turned the "Keep 100% Previews" option on and off, purged and re-built caches for specific folders, and yet nothing new shows up in the "full" folder.
Also, I can't determine what the "full" jpegs are used for. My testing seems to confirm that the thumbnails and previews displayed by Bridge all come from the "256" or "1024" folders. I can't find any case where the jpegs in the "full" folder are used for anything.
Would appreciate others testing on their systems and offering any explanations. I have not tested on old versions yet (still have CC and CS6 installed), so I'm wondering if something changed with the release of CC 2014.
