Doing a second "Convert to DNG" on another batch of photo with different settings will affect the first task already in progress (it will inherit the settings of the second).
Folder 1 with Raw photo's. Do "Convert to DNG...", start converting
Folder 2 with Raw photo's. Do "Convert to DNG..." but with "lossy compression (new Lightroom 4 feature).
As soon as Task 2 starts, it will affect Task 1 (already in progress): It will start doing "lossy compression" on the raw's that where not converted yet.
I observed the difference in file size by accident. Luckily I had a backup.
When you convert one folder of NEF Files to DNG and another folder of NEF files to DNG with Loosy compression the convertor switches the images from the first folder to Loosy DNG's.
This reply was created from a merged topic originally titled
DNG Lossy Compression BUG.