Focusing question

vedaeddy

Hi,

I'm new here so this is my first (but probably won't be my last) question about using the D3200. I just got it about a week ago and I'm slowly but surely trying to figure it out.

I know I am probably making this much more difficult than it really is, but I just can't wrap my head around this whole "holding the shutter down halfway to focus on a subject, then with the shutter still held halfway down, recomposing the frame." I am doing this in single point AF-area mode and AF-S focus mode.

So, is this what that means: if I have a flower pot sitting on a table and I lock focus on it with it being in the middle of my frame, I can then put it all the way to the left or right in my frame and it will remain in focus? Or does it mean than the center of the frame, where the flower pot once was, remains in focus? How about if I choose to get closer or farther away?

HELP!

ohyeahar

This could be a lot to take in. I’ll start by answering your hypothetical questions assuming you’re using Single Point AF-area mode and AF-S focus mode.

“if I have a flower pot sitting on a table and I lock focus on it with it being in the middle of my frame, I can then put it all the way to the left or right in my frame and it will remain in focus?”

Let’s say your flower pot is 5 feet away. You used your center AF point to lock your focus on it. This means everything that’s 5 feet away from your camera is in focus. This remains true as you keep the focus locked and recompose. You may realize that if you recompose your shot, the distance between camera and subject actually shifts a bit. So it’s possible that if you recompose your shot too drastically, you may shift your subject out of the depth of field. You may compensate by increasing your depth of field by doing any of the following: use a smaller aperture, shooting at a greater distance, and/or using a shorter focal length. Increasing the depth of field will allow greater freedom in recomposing without throwing your subject out of focus.

“Or does it mean than the center of the frame, where the flower pot once was, remains in focus? How about if I choose to get closer or farther away?”

No, unless you use Single Point AF-area mode and AF-C focus mode. With those settings, if you keep the shutter half-pressed, the camera will continually try to keep whichever AF point is active in focus.

I would recommend keeping your focus mode on AF-A. The camera does a good job on choosing between AF-S and AF-C on its own.
The 3D-tracking AF-area mode is actually designed specifically for focus-recompose. It works well as long as a you keep the subject on any of the available AF points. It actually will reacquire focus on the AF point you move your subject to, so it will take longer since your camera has to focus again. But this ensures your subject is in focus.

vedaeddy

Thanks for the explanation. I'm learning a little something everyday, and some things that once didn't make any sense become a little clearer so it's all good.