> I recently purchased a Nikon D300 on ebay but when i try to >set the diopter using the grid display on the viewfinder, i >can either get the vertical alignment or the horizontal >alignment correct, but not both together. Could this be a >problem with the mirror being slightly askew. Anybody had this >problem, any ideas. > Thanks > Dave
In case there is not a problem with your screen:
If like me you have astigmatic vision and you remove your glasses, it will be impossible to have vertical lines and horizontal lines in focus at the same time.
Furthermore if you wear multi-focal lenses you need to look through the distant section not the reading portion.