i've been unhappy with the sharpness of my photos. not all. i'm using a nikon d300 with an 18-200mm 3.5-5.6 DX lens. i recently took some posed photos with a model using this combo. when i used the on-camera magnification, i zoomed in as far as it would go and could see sharp definition in the model's eyes and skin. so i'm fine with a studio lighting/posed model situation. the problem is when i'm shooting in situations that are not studio-lit. outdoors or indoors. i use auto-focus much of the time but seem to always end up with the background content in focus, but not the subject. i've been switching to manual focus - i zoom-in on the subject - to focus - then zoom-out to frame the image. but i don't re-focus. the results i've gotten are ... mixed. i viewed the images in the camera - with the magnification all the way in and some are sharp ... others... not as much. is my technique valid? i mean... i'm thinking that if i want to frame the shot at 18mm, but i need to zoom-in to 85mm to get the focus correct, should i re-focus? the problem there is that i can't really finely-sharpen the focus inside the viewfinder when my lens is at 18mm. i'm sure this raises more questions than can be simply/quickly answered... but if we can start the conversation, that would really help me a lot. thank you.