1.8 is wide open. pag close up may tendency na mag blur yung ibang parts ng subject. try setting to higher apertures - f4 to f8. kung naka tripod ang cam, di na problema ang blurred shots. and make sure to set at least a 2 seconds timer before the shutter clicks para di ka na nakapindot.
also, kung gusto mo well-lit yung subject, you need to bathe it in light - isa sa taas, isa sa gilid at harap. yung sa isang side, pwede ka mag reflector.