Issue with ThumbnailImage

[SulG]

Hello,
I am a newbie to ExifTool.
Basically, I am trying to extract a preview and thumbnail from a DNG file.

1)
exiftool -b -PreviewImage IMG_4147.dng > IMG4147prev.jpg
works successfully and generates a beautiful preview image.

2)  However,
exiftool -b -ThumbnailImage IMG_4147.dng > IMG4147thumb.jpg
generates a 0 "zero" sized  IMG4147thumb.jpg file.

Any idea why the -ThumbnailImage tag generates a zero sized file?
I have tried this for various DNG files, I always get a preview image, but thumbnail image is always zero.

Your help is appreciated.

Thanks,
SulG

[Phil Harvey]

Hi SulG,

Sorry for the delay in responding.  I was on vacation.

The problem is that the DNG file doesn't contain a JPEG-format ThumbnailImage.  Use exiftool FILE to see all of the metadata that ExifTool can extract.

- Phil