Lightroom 101 - How Previews Work
Learn essential Lightroom skills from Academy Master Sean McCormack as he gives you the skills to organise and process your images in Adobe Lightroom CC.
In this film Sean explains how Lightroom CC generates previews and how you can adjust these options to match the workflow that suits you best. Lightroom has a variety of options which you can set to automatically generate preview sizes automatically, and then it can generate alternatives on a file by file basis as is required once you begin working with the files. Sean also goes a bit more in-depth to show how to find these files, how they actually work, and how to extract previews in case of critical file loss.
Extract Previews Script link: https://helpx.adobe.com/lightroom/kb/extract-previews-for-lost-images-lightroom.html