For my thesis I have to explore, in the field of psychology of perception, the reasons why the character of realness in CGI's movies won't never be comparable to those of stop-motion.
The specific field is Psycholgy of visual communication and the thesis is based on the fact that stop-motion animation is a form of art so special, in terms of representing realness, that CGI can't never reach it.
I have also to compare a picture of a frame in stop-motion with one in CGI but I can't find two identic characters or objects made with both technique.
If you can help me, I'll really appreciate it!
I think the difference lies in the mistakes that stop motion inevitably has. This is what makes it so charming, and remind the audience that it is real magic, bringing a puppet to life and giving it character.
That and the fact that a shot is not predetermined. With other forms of animation the shot is timed and the most important frames are drawn first, so that the rest become inbetweens. That means that nothing can go wrong and everything goes at the pace the director wanted. It allows for no serendipity.
With stop motion shots you can do rehearsals and write up your dope sheet and time things and still it might go a little differently - the details of moving the puppet are often dictated by the physical limitations of the puppet itself.
It is interesting that CGI movies are trying to introduce some elements that reduce their perfect slickness - dust motes in the LEGO movie for example. But then look at Wes Anderson positively using the 'boiling' of animal fur (in Fantastic Mr Fox and Isle of Dogs) as a characteristic. And Aardman talk about 'thumbiness', meaning the thumb prints that are sometimes visible on their clay puppets. All these things serve to remind the viewer that a person touched these puppets to make them move.
For a combination of CGI and stop motion, have a look at the making of videos on The Boxtrolls, where I think the main character was integrated with a lot of CGI.
In fact, have a good look at LAIKA's output. While it is awesome in scope and masterful in its execution, sometimes the slickness and effects IMHO detract from the enjoyment of the puppetry.
That sounds like a great perception to explore.
Naturally, I was sraight to thinking of LAIKA. When I went unprepared to see Coraline my mind was thrown by how slick was the opening sequence, I actually began to doubt the publicity that it WAS stop frame.
However, although i knew in advance there were significant CG elements in Paranorman, I found the hand-made feel came over much more in that film than the earlier one.
Of course, technologies supporting both animation techniques have come leaps and bounds in the last twenty years. Notwithstanding Simon's point of simple fact that puppets give a unique performance in each take just like real people - I would be interested to hear what others think about the contrast between the massively imperfect Shrek movie and it's later franchises with the same characters.
There are quite a number of threads on this site where this question has been explored, so have a look around at the topics.
It seems to boil down to the errors that occur with stop motion, or rather the perfection of movement in CGI. This can make CGI look a bit robotic and over-smooth. There is a concept called The Uncanny Valley, where something looks very nearly like a real being but lacks in a certain respect, and this seems to trigger a revulsion in a viewer. I would think this is an innate property of our perception - the ability to tell whether something is alive or dead, friendly or foe has been perfected through natural selection. So we are unconsciously expert at picking up on signs that something is not real.
Of course stop motion puppets are not living beings, but they do exist in real space, and the quirkiness they have makes them seem more imbued with spirit. It is also often apparent that they have been touched by hiuman hands, so there is a more direct communication between artist and audience through the character.
The particular power of cinema is that with live actors the unconscious micro-signals in the facial expressions are magnified on a big screen - this IMHO is what separates good and bad actors. Of course a stop motion puppet does not display these micro-signals, but this does not stop that audience from projecting them onto the puppet, so for example a shot of a puppet 'thinking' comes across as such even though everyone knows it is actually a piece of rubber or clay. So we intuit what Gromit is thinking about Wallace as he 'reads' the paper and raises his eyebrows and swivels his eyes. We project the micro-signals onto him. This also happens with CGI and 2D hand-drawn animation, and in terms of the psychology of visual communication it seems to me to be significant as a phenomenon. It is really the foundation of what Walt Disney 'discovered' - that it is possible to communicate emotion through moving drawing etc. Read 'The Illusion of Life' to get more of this.
But when a stop motion puppet remains perfectly still, in a hold, it can suddenly seem 'dead' if it lasts too long without e.g. a blink. I suspect CGI has the advantage here, able to put in tiny movements to keep the puppet 'alive'. And CGI uses increasingly sophisticated means to add a little quirkiness - wiggle factors etc. So the distinctions are certainly not clear-cut.
I know that the Boxtrolls made use of some CGI characters within the film. There are some good 'making of' videos on YouTube.