I don't have the Nikon D810. I downloaded a sample raw image (NEF file) and converted it with the DNG converter. The converted DNG file measured 7360 x 4912 pixels, which is the published dimensions of the large image size for the camera. I am not a highly technical person so I don't understand or care to understand where you came by those other higher numbers. But according to Nikon's published specifications and my conversion of the NEF file that I downloaded, everything seems to be in order.
Thank you for your reply. I appreciate your looking into this. I will explain in more detail how I arrived to my conclusions, for people who care to understand, at the risk of making this post a bit too large.
But before I do that, let me give a little technical background. Most RAW images use a CFA pattern; this means that each pixel captures only one color (R, G, or B). In order for such an image to be converted to a full RGB image, interpolation has to be performed at pixel level for colors that are missing at that pixel. For example, both R and B have to be interpolated for a pixel in the CFA image that captures only G, and both R and G have to be interpolated for a pixel that captures only B, and so on. Interpolation uses values of neighboring pixels that capture the same color. Digital cameras capture images slightly larger than the final image, so that there are enough neighboring pixels at the edge of the final image to use for interpolation and avoid artifacts.
Now back to the numbers. NEF files are TIFF files, which means you can use TIFF readers to peek into them. This is an excerpt from ExifTool output when run on a D810 NEF file:
Image Width : 7380
Image Height : 4928
Bits Per Sample : 14
Compression : Uncompressed
Photometric Interpretation : Color Filter Array
This shows that the size of the original RAW image is 7380x4928. Since interpolators need to produce a final image of 7360x4912, they have 10 extra pixels at top and bottom and 8 extra pixels at left and right of the image to use for interpolation. I would expect the DNG file to retain all the pixels of the original NEF (since DNG processors need to perform this interpolation), but running ExifTool on the DNG file gives this:
Image Width : 7372
Image Height : 4920
Bits Per Sample : 16
As you can see, the DNG keeps only 7372x4920 of the original image, for no good reason. Granted, it still keeps more than the final image size of 7360x4912, so the interpolator should still have, in theory, 6 extra pixels at top and bottom and 4 extra pixels at left and right. However, according to ExifTool, the DNG file also contains this:
Default Crop Origin : 12 8
Default Crop Size : 7360 4912
What this means is that the interpolator is supposed to trim 12 pixels on the left and 8 pixels at the top from the final image (instead of 6 and 4, respectively). This leaves no extra pixels at the right and bottom of the image for interpolation, which is confirmed by dng_validate tool that comes with the DNG SDK:
Since this is only a user to user forum, I doubt you'll get much resolution to the "problem" here. I suggest that you express your concerns on the following forum which is monitored more closely by the developers. You might get more consideration of your concerns and a more meaningful response there.
Thanks Jim! I've posted this issue there.