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Previews - How long do they last?

Richard Ludwig
I'm a long time Lightroom user who has just started using C1 Pro 9 for Sony.
I have been viewing tutorials and searching the online Help but can't find an answer to my question.
It certainly would help if there was an Index in the User Guide to look things up with.
When Previews are generated how long do they last?
I see under File there is a way to Regenerate Previews, so they don't last indefinitely.
Is there a way to set how long previews last?

It certainly would help if there was a fast way to look up things like this - all suggestions appreciated.

Thanks
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Comments

10 comments

Date Votes
  • BeO
    Top Commenter
    Hi Signrap,

    What do you mean by "how long previews last"? A preview is a proxy of the raw file + your edits to be shown in the viewer. Once generated they last as long as they are on your drive, they get updated as you adjust the image.

    Am I getting your point?

    Cheers
    BeO

    Edit: I believe "Regenerate Previews" is rather an emergency function in case the preview looks odd (e.g. by an OpenCL problem)
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  • RichardT
    I also couldn't find much in the online help about previews and regenerating them.

    However, the following article is quite informative even though it was written for V7:



    The article mentions that you can change the size of previews in the preferences. That new size will only affect new imports unless you use the Regenerate Previews option on previously imported images.

    Richard
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  • Richard Ludwig
    [quote="BeO" wrote:
    Hi Signrap,

    What do you mean by "how long previews last"? A preview is a proxy of the raw file + your edits to be shown in the viewer. Once generated they last as long as they are on your drive, they get updated as you adjust the image.

    Am I getting your point?

    Cheers
    BeO

    Edit: I believe "Regenerate Previews" is rather an emergency function in case the preview looks odd (e.g. by an OpenCL problem)

    In Lightroom you can set the Previews to be discarded after a certain period like 30 days (which is the default) or discard them on your command.
    The reason to discard them is that Previews can take up a large amount of disk space and if you have a large catalog e.g. say 50,000 or 100,000 images that is a huge amount of disk space which can make the catalog very large.
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  • Richard Ludwig
    [quote="RichardT" wrote:
    I also couldn't find much in the online help about previews and regenerating them.

    However, the following article is quite informative even though it was written for V7:



    The article mentions that you can change the size of previews in the preferences. That new size will only affect new imports unless you use the Regenerate Previews option on previously imported images.

    Richard

    Richard thanks for the link, very informative.
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  • BeO
    Top Commenter
    Preview size change, good point Richard!

    btw, the preview size should not be smaller than the viewer size. Matching the screen resolution seems to be best practice under normal circumstances.
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  • Wesley
    I think OP asked how long to keep the preview cache tidy.

    Speaking of cache, I don't see an option to purge it.
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  • BeO
    Top Commenter
    I assume the question was mainly raised because signrap is used to it in LR, not so much out of a real necessity, as the C1 Cache is not that big.

    In case I am wrong: The only possibility I see is to delete to preview files from disk. When a collection is viewed in browser C1 will regenerate the missing files though. To save disk space he could (re-)genarate tiny previews for the images he doesn't want to view in viewer very often.

    Finally, finding topics in the documentation:
    - Use navigation panel or search function in the online help
    - Question mark icons in the C1 tools

    cheers
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  • Richard Ludwig
    So I surmise from your collective responses that C1 does NOT have the ability to purge the Preview cache and selectively regenerate previews on just the selected images (not the entire catalog).
    The reason I ask is that I have C1 and LR catalogs on a 512 GB SSD so that my previews are almost instantly available when processing. Right now I have a LR catalog containing about 55,000 images where the previews are deleted after 30 days. I bought my first Sony a7R in the fall of 2014 at which time I started hearing about C1. Since I was so comfortable using LR I waited and thought long and hard before getting C1 after having played with it for a while. I had assumed that C1 would have the same preview purge feature that LR has. I have assumed wrong. At the moment I have only imported a few hundred images into C1 as I wanted to be thoroughly familiar with its working before importing 8-9000 images I have taken with my Sony's. I'm just about at that point but I wanted to clear up this last major question about previews before I made the move. Thanks for you help and insight.
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  • RichardT
    If you select the "All Images" collection and then "Select All" (Ctrl+A) it may be possible to Regenerate Previews for all the images. However, on my system the "Select All" operation is taking ages, so I have no idea how long it would take to do the complete regeneration.

    At the moment the space taken up by the preview cache doesn't worry me. I have a single catalog on a 500GB SSD. The catalog currently references 33608 images files that occupy approx 530GB on a separate HDD. The preview image size is set to 2560px and the size of the preview cache folder is 51.8GB. I still have 267GB free on the SSD.

    Richard
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  • Wesley
    Looks like we have to manually delete each cache folder (if you're using sessions) and than regenerate previews if you ever work on them again or CO might do it automatically.
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