So I just got my new 28-75 tamron, and it takes tack sharp pictures, but through the viewfinder the image is blurry, I cant manually focus, but when I use the AF its super sharp but still.. cant seem to see straight from the viewfinder waa its driving me crazy, I know it might sound retarded but I need some heeeelp!
There should be a little wheel,lever, or some kind of switch on the side of your viewfinder, play with that until the image becomes clear when you are looking through it.
The best way to set the diopter (the little viewfinder focusing wheel) is to look at a single colour scene (the sky, a white wall etc...) and then adjust the focus so that it is totally out of focus. You then adjust the diopter wheel until the AF boxes in the viewfinder appear sharp to your eye.