How does the Nikon D40 choose an autofocus point, and how can I control it?

Asked 7/22/2010

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My Nikon D40 often seems to focus on the wrong part of the scene when it selects the autofocus point automatically. How does the camera decide which of its AF points to use, and what’s the best way to make sure it focuses on my intended subject?

nikon autofocus focus-points technique nikon-d40

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

16y ago

2 Answers

The camera makes a best guess as to what it thinks is the primary subject of a photo. Given that the camera has multiple (three) autofocus points, sometimes it guesses wrong. There are a couple ways to overcome the fact that autofocus can't always guess where you'd like the focus point:

Manually choose the correct focus point and compose your scene so that your subject is at that focus point
Use a single focus point (usually the center) all of the time, and set your focus using that point and then recompose your scene.

Originally by user89. Source · Licensed CC BY-SA 4.0

user89

16y ago

AI Answer

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In automatic AF-point selection, the Nikon D40 is basically making its best guess about your subject. Based on the answers here, it tends to favor a nearby subject and/or a focus point with strong contrast, so it can easily choose a different area than you intended.

The usual fixes are:

Select the AF point manually so the point sits over your subject.
Use a single AF point only, often the center point.
Focus-and-recompose: place the selected point on the subject, half-press to lock focus, then recompose and fully press the shutter.

This is normal behavior for entry-level autofocus systems: the camera can’t always know which object in the frame matters most to you. If it keeps picking the wrong spot, manual AF-point selection or center-point-only AF is usually the most reliable solution.

How does the Nikon D40 choose an autofocus point, and how can I control it?

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