The first copy of it I received wasn't even cutting it at +20! Had to go back at that really. The one I got in return seemed fine straight out the box, to my eyes. Then I tried the method someone posted on here, the green dot in VF/live view manual focus method - and that suggested I should dial in +13 on it, which I have done, and it seems spot on! Either my eyes are going wonky! or the difference is so slight you can only tell at extremes.