Lightroom
renders three types of previews: thumbnails, screen resolution images,
and 1:1 previews. 1:1 previews have the same pixel dimensions as
the original photos. All previews are stored in the folder where
your catalog is located.
Choose File > Catalog Settings.
Choose from the following menus:
Standard Preview Size
Specifies the maximum pixel dimension for the rendered preview.
Choose the size that accommodates the display size you’re working with.
Preview Quality
Specifies the appearance of the previews. Low, Medium,
and High are similar to the upper range of the quality scale for
JPEG files.
Automatically Discard 1:1 Previews
Specifies when 1:1 previews are discarded. 1:1 previews
are rendered as needed and can make the library preview file large.
