Sandman
The *only* point Lightroom loads the original file and applies the rendering chain in RAM is when you're viewing an image in 100% zoom.

Eric Stevens
Or when you export the image.

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.

Eric Stevens
I know that

but Sandman seems to disagree.

That's why I asked him that particular question.