DNG File size on export

After importing a RAW image into Topaz Photo 2.0.1, via Plugin extras, then sorting out the noise and sharpness, when I then export the DNG back to Lightroom, the file size has gone from 38.7MB to 171.5MB. This is madness. Please explain why this happens and how I can export back at a file size similar to the original.

There are many posts explaining this on the forum. Do a search and you shall find them.

In short though a RAW file contains sensor data and a full size preview … the DNG output is of the resulting image file (not sensor data as only a camera can do that) and uncompressed, you can compress it using the Adobe DNG converter, but it is lossy.

Typically the file size is the same as a high quality TIFF file. Remember the DNG is NOT a RAW file, only cameras can produce them.