I bought to shoot a baby, without a flash. From the flash, they have a clouding of the lens and other troubles. So, in order not to write too much: I also thought that his sharpness starts from aperture 4, etc. Nothing like that. It was just necessary to adjust the back focus in the fotik. The fact is that at aperture 1.8 there is a very shallow depth of field, and the slightest mistake leads to blurring. Now everything is fine at 1.8. So, before scolding, check your camera + lens combination. I myself shot for several years with other lenses (not so fast) and did not even suspect such a problem. Fotik d50.