Recently, I came across a couple of 'sketches' which has proportions that are virtually indistinguishable from show-accurate vector traces from MLP. Even more interestingly, the pose copied down to the smallest detail if you scale the work down appropriately and put a transparent overlay on top of a past work of that same artist.
I won't mention any names, but I think it was an obvious trace. Here's a fun thought: what are the chances they were actually referenced instead of tracing?
If it was virtually 100% accurate when the vector was overlaid on the drawing then it probably was a trace. Anyone that is skilled enough to do that would put it in their own style instead of copying the shows. Like I said though, virtually. There is a chance that it wasn't traced, but I'd place my bets that it was.
Of course for those special people with a good memory. Its pretty much possible.
Here is stephen wiltshire drawin rome. Its been awhile, but I remeber seeing this guy on yahoo pages. [link]
Thats pretty much down the millimeter without a tool or ruler.
There is also the generas of photorealism, or hyperealism. Search via google. There is also matt painter who do a good job too.
But as for perfection, most of the artist pretty much are trickers of the eye. We could paint many strokes, and tediously it can look accurate from far away. This is a good reason why you should go to musuems, because looking at a big painting from both far away and then studying it up close make a huge difference. From far away, it can look realistic but up close its just alot of various painting strokes.
Reminds me of some really great digital works I've looked at on dA for the purpose of judging them to see if they're something my group (mentioned in my sig) is looking for. Sometimes, I see some REALLY sloppy craftsmanship that's only visible if you look at it in its largest resolution.
Especially with people who use the grid method. They put a grid over the refrence pic, and then put a grid on the thing they are drawing on, then transfer square by square.
And even if it is possible, that's hardly a talent worth developing. A real artist needs to be able to reduce 3 dimensions down to 2 for most forms of visual art. (Sculpture being an obvious exception) And the time spent getting that accurate reproducing a photo or other 2d image is time that could have been spent on actual useful things.
Really the only way you can confirm a trace is to get the source and sit it right next to the artwork.
I don't feel there is any need to be technical with (be it using a grid, copypasting, or eyeballing) a trace when it's obvious that the artist did not create any conceptual part of the piece themselves, be it the pose, character, or the image itself.
I won't mention any names, but I think it was an obvious trace. Here's a fun thought: what are the chances they were actually referenced instead of tracing?