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Catalogs Purge cache button

craig_k

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Upon getting the new install preferences built, Under Preferences: file handling tab, I see the cache settings which reflect maximum size at 40 gb camera raw and 3 gb for video, would one want to purge those caches for any reason to be beneficial in some way? ( i don't know what they do exactly ) I would think i would like to increase the sizes to accommodate huge catalog inventory and not uncommon to have 3000 image new shoot imports, on a daily basis.
 

LexS

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They are just as it says: cache. You can purge them. 40 GB is very very high, is that what you need when working on your files? I have 3GB, and that is way more than I need as buffer.
 
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I've never understood the default cache settings. It is my understanding that ACR cache is where ACR stores the RGB image that it constructs from the RAW data file. As such 40GB would barely hold one camera card full of RGB data. ACR is self purging so that when the caches is full ACR drops the oldest entries to add new. This too seems to defeat the purpose of a "purge cache" button.
 
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Each ACR cache entry would typically be between 1 and 2mb in size, thus 40GB would hold between 20,000 and 40,000 entries. As the cache also works on a FIFO basis, only when opening much older images from the catalog is one likely to encounter a missing ACR cache file with it's attendant few seconds loading delay. My cache setting it 10GB, which is more than adequate for my relatively small catalog.
 

Gnits

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Interesting.

What info would be stored in such a small cache file. I always assumed it was a work area for temp results as a raw file was rendered. Can understand multiple cores creating / using cache data when batch processing multiple raws. I would really like to understand this better so I can set my own cache sizes appropriately, on my main machine and travelling laptops.
 
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Each ACR cache entry would typically be between 1 and 2mb in size, thus 40GB would hold between 20,000 and 40,000 entries. As the cache also works on a FIFO basis, only when opening much older images from the catalog is one likely to encounter a missing ACR cache file with it's attendant few seconds loading delay. My cache setting it 10GB, which is more than adequate for my relatively small catalog.
Thanks for that explanation. It is the 1-2mb per entry that I find unexpected. How does a large 48mp compressed RAW image end up being described by a 1-2 MB RGB image?
 
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They don't have to be massive files if their primary purpose is to put a updated image in front of the user while waiting for the "real" image to be created in the background. I just exported a 45mp file which weighs 58mb, quality 70, long edge 1024 and it produced a jpeg of less that 300kb. An ACR cache entry would be different in ways I don't fully understand as it would need to be able to respond like a raw file when moving sliders in the basic panel, so I'd expect it would be larger than 300kb, but not massively so.

Examining my own ACR cache, there are plenty of the *.dat files less than 1mb each (I'd say the majority are like that), but there are some heavier files (one in excess of 10mb), not sure what that would relate to.
 

craig_k

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I certainly appreciate the input received, thank you sirs.
 
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