I've been adjusting the Diotric Adjustment for the viewfinder on my 350D and am struggling to get the focus points absolutely sharp.
According to the manual (page 42): Turn the knob left or right until the AF points in the viewfinder look sharp.
And... If the camera's dioptric adjustment still cannot provide a sharp viewfinder image, using Dioptric Adjustment Lens E (10 types, optional) is recommended.
Now, whilst I don't claim to have 100% perfect eyesight I do think my eyesight is better than average and would expect to get the focus points sharp in the viewfinder.
I'd appreciate any other users' feedback, many thanks,