About every third time I am called upon to look through someone else’s digital SLR camera, whether teaching, trying to troubleshoot a problem, or to take a photo for them, I look in the viewfinder and see this…
Immediately I recognize that the diopter control, which moves the little adjustable optics between the eyepiece and the focusing screen, has been mis-set, usually to one of its most extreme positions.
Diopters many years ago were screw-on attachments to the viewfinder that came in various increments, like -1 or +3, that you could install so someone who wore prescription glasses could see the viewfinder clearly without their glasses. In recent years, the diopter control has been included in almost every camera with a viewfinder.
When I see this maladjustment in someone’s camera, I usually say something like, “Your diopter is set really strong.”
The reply is almost always, “My what?”
It turns out that most people have no idea this thing exists, and at some point either accidentally or while playing around with their settings, managed to set it to one extreme or the other. If it’s a student, I’ll explain the use of diopter settings, set it back to a normal setting (which is easy – just move it until the display items in the viewfinder look sharp), and give the camera back to them.
They always say, “Wow, that’s much better!”