I try to keep my masterpiece production down to a few a week. 😉
By definition a masterpiece is work at a high level as determined by a group of peers. So who determines if something is a masterpiece? I don’t think it is the artist, although the artist who knows their craft certainly has a feeling for which works they are most proud of and the level of skill that was required to achieve the result.
It is other photographer’s or artists, art professionals and ultimately collectors who determine something’s value.
As an individual artist selling mainly through unfiltered means, i.e. self-publishing my main feedback loop comes from buyers. They are the ultimate judges of if a work is good or not. What I would consider a masterpiece sometimes matches up with what the buyers want and sometimes it doesn’t.
You can see all of the images, art, design and photography that has sold on Fine Art America and Pixels in this collection – https://pixels.com/profiles/edward-fielding.html?tab=artworkgalleries&artworkgalleryid=240882
Other judges are the curators of my rights managed stock images on ArcAngel and the designers who license my images for book covers. They of course are using a different standard of “masterpiece’ than consumers.
I also have interior designers purchasing from Designerprints.com which are buying from a different angle than consumers. Often these purchases end up in hotels, restaurants and office buildings. These designers have a different idea of what a masterpiece for their purposes is all about.