Sandman
Depends on how you export it. If you export it as a low-res highly compressed JPG, it can use the preview file. Chances are that it doesn't, but it certainly could, since the preview file *is* the current pixel data of the image.

Eric Stevens
So what happens when you want a high quality TIFF of the same size as the original file? Do you expand by resampling your low-res highly compressed JPG?

nospam
questions like this mean you don't understand how it works.

it *always* uses the original data. the cached previews are a speed optimization for the user interface.

Sandman
Well, yeah. Every photo you look at in Lightroom is data from a preview file. Lightroom creates three preview files for every single photo in its catalog.

1. Thumbnail - used in grid views 2. Standard preview - created if your monitor is smaller than 2048 pixels wide, used in all other modules, except the develop module and loupe 3. 1:1 - used in all modules if you have a large monitor, always used in the develop module and in the loupe.

Every single time you're looking at an image in Lightroom, you're looking at a preview file.

Eric Stevens
Which I previously described as a simulacrum.