Building Image Previews in Lightroom-->
Importing your photos with the 1:1 preview size selected will result in Lightroom taking even longer to complete the import process than would have been the case if standard-sized had been chosen. 1:1 previews also take up significantly more disk space than standard-sized preview image. I would only use this option if I were importing one or two images and doing a great deal of work I needed to see in every exact detail.
If you're not going to be working on the photos immediately after import but do need to get them into Lightroom as quickly as possible, your best option will be to choose Minimal import option. Once the photos have been imported choose either Render Standard-sized Previews or Render 1:1 previews from Library module Library>Previews menu.
These posts are part of a series: Introduction to Adobe Lightroom