I have recently started using Nikon Capture NX-D to "pre-convert" the RAW files of my Nikon D750. The Nikon software just does a great job with the colors and camera settings, etc. In a second step, however, I import the images into Lightroom, which is obviously the richer tool for fine tuning.
I have tried two paths to do this:
1. Export the RAW file as a JPEG from NX-D
2. Export the RAW file as a 16 bit TIFF from NX-D
When I import the JPEG and TIFF into Lightroom and then export both as JPEGs, I notice that the JPED-based JPEG file is significantly larger (from 1/3 larger up to twice the size) than the TIFF-based JPEG file. However, the quality seems to be almost identical. At 100 % the difference is imperceptable. At 200, 300, 400, 500 % some difference becomes visible but is basically negligable (and at that level of maginification the slightly less detailed TIFF-based JPEG doesn't necessarily look worse to me).
Does anybody have an explanation for such a big difference in file size with hardly any difference in image quality? Am I missing something? If anything, I would have expected the difference in file size to be the other way around, with the lossless TIFF file as a base producing the larger JPEG file with more detail.
If there is truly no (noticable) difference in quality, I would of course prefer the smaller files to save disk space. Even for large scale printing I guess the difference would be imperceptible.
I am attching two sample images (TIFF-based JPEG and JPEG-based JPEG) and screenshots of their 100 % and 500 % magnification.