Adaptation with Films

Adaptations in their many forms can make or break the memories we hold so very dear in our hearts of those stories and the lessons they taught us. Looking at the article, I was very surprised to see just how much work movies have to put in to convey all of the emotions and the meanings behind their adaptations. An example of this kind of effort is the realism that is sought by the fans and the people who see these movies look for in the environment that the movie ties place. The people already have an idea of what the setting and the environment have to look like, what they want is to see that idea of  the environment before their eyes. The set coordinators have to make this common idea flourish and express every little meaning that the environment is suppose to do as the original text does. Other things such as lighting, costumes, the body movements and even the voices of the actors (both main and supporting) are all important in giving the audience the experience that they were hoping for and expressing the same ideas. The Mise-en-Scène can be done many different ways, from a naturalistic view to a theatrical, with the props playing important roles and pushing themselves out from the actors. The scene can also be important on its historical accuracy in some films, such as those that take place in the far far away galaxies, the rugged western trails, or by the columns of ancient cities that housed empires. Now knowing that all of these different elements are needed to be accounted for in creating the scenes can make my analysis of films much more effective in determining whether or not the adaptation is true or altered from the original and if the adaptation is a threat to the original.

My question is this:
How do you determine if an adaptation is doing harm or good to the original source material and can this effect the way that the lessons and values from the original are translated?