Mark, if you are making the jump from the old days of completely manual cameras to the ever evolving world of digital photography I can commiserate with you. Everything you know about exposure and composition will still be valid but the abundance of controls that the new cameras have can be perplexing, to say the least. You have had some good suggestions about using single point focus and finding an aftermarket manual about your camera model. The camera manual that the manufacturer gives you tells you what each button does, the aftermarket book tells you the why, how and when part of it.

One thing I would suggest is that you choose to use either back button autofocus or shutter button AF and not have both active at the same time. If you use the BBF to tell the camera what you want to focus on, reframe and then press the shutter button the lens will refocus on whatever is covered by the focus point.

The more you know about the autofocus and exposure systems of you new camera the better off you will be. Coming from a totally manual system you will need time to learn what you can safely allow the camera to make decisions about and what you need to control yourself. Relax and have fun!

I came out of the dark ages of film photography with a good practical background & a degree in photo tech. I wanted to get back into photography, so I bought a D7100 with the 18-105 kit lens. That was all I could not really afford at the time, so it's the only lens I've got. I think I'll be happy with it if I can figure out the autofocus issue I'm having. I have my AF on my back button, altho it happens on the shutter button as well.

"Back in the day" all I had to do to focus, was aim at my subject and use the manual ring until it was in focus. Easy. Now, it doesn't seem like the camera has a clue of what the subject is, shows numerous rectangles in the viewfinder until it settles on one. Going thru the same motions with the same subject can get a different number of rectangles and the single rectangle always settles in a different spot. And never on the subject matter. Maybe close, but usually several inches off. Sometimes you can hear the AF motor working and when it stops, there's nothing but blur.

To get your subject in focus, how do you tell the camera what the subject is so it can autofocus on it? So who has the adjustment problem: the lens or me? Somebody, HELP!!

The D7100 is a great camera.
If you look to the lower left side, just below the lens you'll see the switch labeled AF. M. that controls the auto focus or manual focus without going into the menu's. When you press the button in the center of the switch, while holding it in you can change your focus settings by turning the rear command dial, that will set the camera to AF-A, AF-S, AF-C. The front command dial will set the number of focus squares. If you set the setting to AF-S you can adjust where you want the focus square with the toggle button on the back of the camera on the right side.

You can You Tube "D7100 Focusing" , there are some good video's there. Good Luck.

I came out of the dark ages of film photography with a good practical background & a degree in photo tech. I wanted to get back into photography, so I bought a D7100 with the 18-105 kit lens. That was all I could not really afford at the time, so it's the only lens I've got. I think I'll be happy with it if I can figure out the autofocus issue I'm having. I have my AF on my back button, altho it happens on the shutter button as well.

"Back in the day" all I had to do to focus, was aim at my subject and use the manual ring until it was in focus. Easy. Now, it doesn't seem like the camera has a clue of what the subject is, shows numerous rectangles in the viewfinder until it settles on one. Going thru the same motions with the same subject can get a different number of rectangles and the single rectangle always settles in a different spot. And never on the subject matter. Maybe close, but usually several inches off. Sometimes you can hear the AF motor working and when it stops, there's nothing but blur.

To get your subject in focus, how do you tell the camera what the subject is so it can autofocus on it? So who has the adjustment problem: the lens or me? Somebody, HELP!!

I came out of the dark ages of film photography with a good practical background & a degree in photo tech. I wanted to get back into photography, so I bought a D7100 with the 18-105 kit lens. That was all I could not really afford at the time, so it's the only lens I've got. I think I'll be happy with it if I can figure out the autofocus issue I'm having. I have my AF on my back button, altho it happens on the shutter button as well.

"Back in the day" all I had to do to focus, was aim at my subject and use the manual ring until it was in focus. Easy. Now, it doesn't seem like the camera has a clue of what the subject is, shows numerous rectangles in the viewfinder until it settles on one. Going thru the same motions with the same subject can get a different number of rectangles and the single rectangle always settles in a different spot. And never on the subject matter. Maybe close, but usually several inches off. Sometimes you can hear the AF motor working and when it stops, there's nothing but blur.

To get your subject in focus, how do you tell the camera what the subject is so it can autofocus on it? So who has the adjustment problem: the lens or me? Somebody, HELP!!