Originally posted by normhead I've seen a scientific paper suggesting there is no advantage 14 bit over 12 bit on APS-c sensors. It's just there to mimic the 14 bit on FF. But, if you choose to show us a few examples, I'll ignore the science and go with the practical. I've personally shot 12 bit and 14 bit side by side and could't tell the difference, and I don't know anyone who has been in a situation where they have.
For photographing artwork I would think the Tamron 90 macro would be the way to go. Those longer focal lengths usually have less distortion. I wouldn't go narrower than 50mm, the Tamron 90 just happens to be a great deal. I'd use my Sigma 70 macro myself, but it's a bit more money, and has been discontinued.
I should probably mention that I'm an r&d engineer in the film visual fx industry, so I too have read one or two scientific papers in this field
There is a reason why many films are still shot on film: colour accuracy and speed. (Yes digital cameras are used, but not as much as you might imagine)
Can you take a good shot with 12bits? Absolutely. Can you edit it in Lightroom to get a great image? Absolutely!
However, this is not an issue of taking a great image, it's a problem of colour perception and representation; and colour perception is *not* scientific. If it was, you'd have no need for white balance (yes those whites are actually blue in daylight, and yellow under artificial light!), and film users would have no need for tungsten/skylight filters.
Your brain plays funny tricks on your colour perception, and so by it's very nature it is entirely subjective. When I take a photo, I edit it to make the colours better than they are in reality. If however you are an artist who has already decided upon the colour palette, then all you really want to do is reproduce that as closely as possible.
Here in lies the problem. If you have trained your brain over a number of weeks to a certain colour palette (as an artist would do when painting an image composed of 'faint colours'), then any digital version will need editing to match your perception of the original. The question is simply how much editing do you want to do?
If the OP had mentioned artwork which used bold & vivid colour palettes, then 12bits would probably be fine. But for subtle shades, you will be best served by 14 bits. (Incidentally, if you watch a film that is highly saturated, or quite dark, it's usually because the vfx company is under pressure to deliver the results quickly)
The phrase 'you can do anything in post' is only half true. You can, with effort, but having high quality source material makes the job much easier. Now maybe because I've been staring at images coming from multiple sources (different film stocks, different sensors, cg elements, etc), and have been staring at the composited and graded results on monitors capable of displaying 10bits per channel, maybe I'm just overly sensitive to this; but I still maintain that it's easier and quicker to get pastel shades and skin tones from a 14bit source than a 12bit one.
I am aware this is entirely subjective, but to my eyes shooting a portrait using 12bits feels like I've shot it on ektar; using 14bits feels much more like portra. I can edit both to make them look good, but one requires less editing than the other.