<p>Greg, Andrew thanks for your comments - that is exactly my point. Both files are up-sampled to the same 16-bit photoshop space. If I paint a gradient at this point and start playing with it, the *painted gradient part* of the image is obviously smoother than the same process repeated within an 8-bit space. I can see the superior 16-bit result in line with my expectations and the difference is obvious.</p>
<p>BUT... what I don't get is the actual captured photo itself.</p>
<p>Forgetting filters for a moment, if I take an 8-bit photo and convert to 16-bit, next take a 14-bit photo and convert to 16-bit (which is effectively what I did in the steps above), would it be reasonable to expect the photo itself to hold more data/subtle tones "hidden" within the image? If I then applied the same extreme posterization side by side, to the point where both images are pushed to reveal banding and grain, should the converted 14-bit version not be at least slightly better than the one originating from an up-sampled 8-bit? In other words, if the camera originally "sees" and records 14 bits worth of tonal variation, should the resulting high-bit TIFF not be visibly superior to an up-sampled 8-bit, following all the editing?</p>
<p>I cannot see any difference: it is as though both sets of outputs (the 8 and the 16 bit TIFF) contain identical amount of actual image data. The "16-bit" TIFF which I am outputting from Nikon simply appears to have 6 bits chopped off, then 8 bits of extemporaneous data appended to it. Hence, when both are edited side by side in 16-bit space, there is zero difference. This would seem to indicate that somehow the RAW data is internally clipped to 8-bits before it even "leaves" the Nikon domain, regardless of which TIFF bit rate you ultimately choose.</p>
<p>As I said originally, maybe I'm missing something here. It's not gonna ruin my sleep but if I'm right, then folks have been exporting 8-bit images to photoshop all along, mistakenly assuming they are "high-bit" when in fact, the only "high-bit" elements are Photoshop-generated artefacts like gradients and effect filters - NOT the actual images you start off with.</p>
<p>Please prove me wrong...</p>