Why does my Nikon D7100 hunt for focus on a bird behind foreground branches?
Asked 12/19/2022
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I’m using a Nikon D7100 with a Tamron 18-400mm lens in autofocus. When I try to photograph a bird perched on a branch behind closer branches or twigs, the focus snaps back and forth and won’t lock on the distant bird. What causes this, and how can I get the camera to focus on the bird instead of the foreground?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
3y ago
2 Answers
3
The camera does not know what you want it to focus on.
Most pictures are easy to focus correctly. Everything is roughly at the same distance. Or, for portraits, there is a big face in the foreground. Here, there is no clear main object, and the camera has to guess.
You can help the camera by using different autofocus modes (e.g. single point), and by selecting a focus point.
The camera uses one or more focus points to measure focus. Note that the area indicated in the display is only an approximation of the area covered by the sensor.
The branches might move due to wind. The camera is also moving slightly in your hand. So, branches are moving in and out of the sensor area(s), and the camera tries to adjust accordingly.
Workarounds:
- Use manual focus.
- Switch to manual focus when the bird is in focus.
- Usually, there is a button to hold the focus. Or:
- Assign autofocus to a button, so you can tell the camera when to focus and when to stop.
Originally by user59825. Source · Licensed CC BY-SA 4.0
user59825
3y ago
0
Generated from our catalog & community — verify before relying on it.
This is normal autofocus hunting. The camera only sees contrast under its AF points; it doesn’t know you want the bird instead of the nearer branches. If twigs or leaves enter the AF area—especially if they or the camera are moving slightly—the lens may keep switching between near and far subjects and fail to lock.
To improve this:
- Use a more selective AF mode, such as single-point AF.
- Manually choose the focus point and place it on the bird.
- If autofocus still gets confused, switch to manual focus.
- You can also “help” the lens by getting focus closer to the bird first, then letting AF finish.
Also note that the marked focus point area in the viewfinder is only an approximation; the actual AF-sensitive area can be a bit larger, so nearby branches may still influence focus.
With lenses like this Tamron superzoom, don’t force the focus ring unless the lens is switched to manual focus, since full-time manual override may not be supported.
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UniqueBot
AI3y ago
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