LR5 1:1 Previews workflow question

Question

I don't work with 1000's of images at a time, so I build 1:1 previews on import to speed up the editing process.  After editing, I do want to discard the 1:1 previews to save disk space, and I usually do it manually on the keepers and have the prefs to delete after 30 days as well.  My question is:  If I delete an image from the disk before I discard the 1:1 preview, does the preview data automatically get deleted from the catalog file as well?  Or should I delete the 1:1 preview first before deleting the image from the disk?  Does it even matter?  I'm just not sure how the catalog preview data gets synced with a photo when it gets deleted.  Thank you.

Answer 1

No, I'm afraid you're not reading my explanation right....so let me try again.
When you work in the Library module, you are seeing what are effectively jpeg previews of your raw files (assuming you are using raw of course, though the same principles apply for other file types). These can be built at several points, e.g. import or post-import, and can be built in several sizes, e.g. minimal, standard, 1:1. When you open an image in Library LR will fetch and load the appropriate preview for the size of the image display area and the zoom factor being used. If one doesn't exist for the viewing mode (e.g. zooming to 1:1 when no 1:1 previews have been pre-built), there will be a delay whilst it is built.
When working in Develop, however, those previews aren't used (except momentarily when you first select an image). Instead the raw file is converted, and the converted image "preview" is cached only, and this is what you see on your screen, and which is then updated in real-time as you move sliders. Note that this reading and conversion of the raw data happens every time you load an image into Develop (apart from maybe the last one or two images which might still be in the cache if you go back to them). In order to help speed-up this conversion, a variety of methods are used....for DNG files there is the option to build "Fast Load Data" which is written into the DNG header during initial conversion and then read when you open the file into Develop. For proprietary raw files there is the ACR cache entries, which are small files (similar to the DNG Fast Load Data) containing partly-processed raw data. This is a very simplified explanation of the process, which with LR5 is further complicated by the introduction of Smart Previews.
OK, the issue here is: when are those ACR cache entries for proprietary raw files created? As I tried to explain earlier, an off-shoot of the rendering of Standard or 1:1 Library previews is the creation of the ACR cache entry (if one doesn't already exist). However, when you open a file in Develop and Lightroom finds that there isn't already an ACR cache entry it will be created then at the same time as the full raw conversion is done. In other words, every time the actual raw data is read, be it Library preview rendering or Develop image loading, Lightroom checks for the existence of the ACR cache entry and creates it if it's not already there. Which is what I said earlier.
It logically follows, therefore, that opening a file into Develop when the ACR Cache entry isn't present would be slower than if it does already exist (though you might struggle to see the difference).
Now does that make more sense? And it doesn't contradict elie-d.