My apologies for the proceeding post… stupid operator error! The correct post follows the right below the quote from John Ellis' post:
That's curious -- I don't observe that in my LR 12.1 / Mac OS 12.6.1. When I select Full Size and Use Lossy Compression on a TIFF:
View attachment 20094
the DNG has a full-size preview, which my Xnview displays.
I verified that whether or not Use Lossy Compression or Embed Fast Load Data is enabled, LR is embedding a pyramid of previews in the DNG, up to full size:
256 x 171
512 x 341
1024 x 683
2048 x 1365
5616 x 3744
$ exiftool -a -G1 -imagewidth -imageheight 20191219_092356.dng
[IFD0] Image Width : 171
[SubIFD] Image Width : 3744
[SubIFD1] Image Width : 683
[SubIFD2] Image Width : 3744
[SubIFD3] Image Width : 1365
[SubIFD4] Image Width : 341
[SubIFD5] Image Width : 171
[IFD0] Image Height : 256
[SubIFD] Image Height : 5616
[SubIFD1] Image Height : 1024
[SubIFD2] Image Height : 5616
[SubIFD3] Image Height : 2048
[SubIFD4] Image Height : 512
[SubIFD5] Image Height : 256
Well, this is curious, indeed. I used exactly the same settings on my conversion to a dng.
Looking at the output from exiftool of an image, it appears at first glance that my photo also has a number of different preview sizes:
But now look at the screenshot from within XnView of the DNG file and the TIFF file from which it was created:
You can see that the image dimensions of the dng file are reported to be 192 x 256.
And now looking at a different part of XnView, where the image file in the dng is also shown to be 192 x 256:
And then finally, looking at the image itself within XnView with View set to real size:
One sees a small image with a lot of white space around it.
I don't really know what to make of this… John's image as well as mine have a number of preview sizes contained within it. But for me, XnView it's only picking up the smallest size. This suggests to me that there could be a setting someplace in XnView that controls this, but like John, I am completely new to the app and therefore I don't know my way around it.