It used to be that if one isolated a part of a file and copied it with Cmd+C (I am on a Mac) and then Cmd+N, then the new document would be the size of the part one had isolated. And then one could paste in the part one had isolated and it would fit exactly, Not any more – instead the new document is, well I don’t know what it is, but it is not the correct size.
Jain Lemos, a Photoshop professional in the Adobe community forums provides the answer:
Please try checking Use Legacy “New Document” Interface in Preferences on the General tab.
And Cory Schubert, an Adobe employee, answers similarly in June 2022.
And I reset the preferences in Photoshop yesterday, and then was befuddled again by the copy paste problem. I googled it and found many people ask the same question over and over. And I forgot for a while that I had found how to solve it and forgotten I had found how to solve it.
More than that though, I discovered today that a lot of people use the function and are copying and pasting a crop of an image.