This is purely an observation from my point of view but whenever i see a study or painting based on a masterpiece or a screen plate. The results are almost in every case very good.So this tells me that our ability to copy is quite good and its not really required to be a high level artist.Junior level to mid level ones can pull this off easily too. Everything you need to know is already in the image we are trying to copy so it becomes a recipe for us.
the important thing though is to not "copy" it but to understand it and deconstruct a work method from it.And if you understand that then the work based from your own mind will be alot better.
When i see this kind of work , for me its not the level of detail and accurcy that one puts in the copied artwork that impresses me, but the images based on that learned knowledge afterwards. And to tell you the truth not many people understand this knowledge or are aware of how important it is to understand it.But the interesting phenomenon is that still during a copy almost a majority who attempts it do well. The values match, the contrast match. So that should tell you that you HAVE the ability to do it, you just need to understand the work behind it.
Many people jump straight inte detail , full scale and about making something sensational rather then thinking about it, i cant stress this enough but understanding why you are creating somethign and how is absolutely the most important things.
if you find mastercopies or simple studies do paste links in here and you can see that all of these are really quite well executed.
here area few pointers to consider when working with studies, copies
* step back from the painting a couple feet and view it as a thumbnail, which are the key values
* how does the artist work out his composition, what is the visual path
* where is most focus put on
*figure out the lighting and relations in the environment
* how does he pose his models, and why
*dont study small detail things, these are technical details not overall understanding