What is an alien DNG?
A native DNG is a DNG created in camera. So it's the original RAW file the respective camera writes to the card.
An alien DNG is a DNG created for instance through the DNG converter or exported from Lightroom or other softwares.
Here is a native Leica-M9 DNG file from imaging-resource.
I've converted it with the latest DNG Converter (version 188.8.131.52).
I've tried several DNG versions (version 2 all the way to version 7.1 … basically they all look the same and have the same file size. So below I only refer to the V7.1 conversion):
Attachment 1 shows the prefs used for the conversion and below a screenshot from the finder showing that the native DNG size from the camera is 18.3MB while the converted version is only 10.2MB (with full size JPEG embedded it would be around 12MB). I don't think the reduced file size comes only from compression. I assume some proprietary data has been skipped.
Attachment 2 shows the Metadata C1 is reading from the files. At least the lens info has been altered.
Attachment 3 shows the native camera DNG file (on the left) compared to the converted DNG file opened in Capture One.
The colors are very different. For the native DNG file C1 applies a Leica M9 input profile while for the converted version it applies a "generic DNG" input profile. If I would assign the Leica M9 input profile to the converted DNG file colors would look totally weird.
Attachment 4 shows that the converted version also looks a bit harsh compared to the native camera DNG (at least when the same sharpening settings are applied)
In Adobe Softwares you won't notice any difference between the files, of course.
1.) quite obviously Capture One handles DNG really well - as long as they are native (camera-) DNGs, so unaltered
2.) Capture One handles converted DNGs ("alien DNGs") pretty weak - even converted DNGs that originally come from a camera that utilizes DNG as its native RAW format
So either Capture One can't read certain proprietary data from converted DNGs … or the respective data is simply not contained anymore in the converted DNG.