I am worried that I am not getting the best focus when using the groundglass with and without movements. I use a loupe to check the corners for sharpness, but I can only check one at a time.. I get one corner in critical focus, then I check the next corner. But how can I verify that a second corner cannot be any sharper without throwing off the focus of the first?
Perhaps I need to attune my 'sharpness memory'? Does ths get easier with experience?