Why does a Canon 1100D lock focus quickly but produce blurry shots in low light with AI Servo?
Asked 1/15/2013
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I was photographing birds on a dull, low-contrast afternoon with a Canon 1100D and EF 400mm f/5.6L. I had the center AF point selected and was using AI Servo. The camera seemed to lock focus quickly, but all 150 shots were badly blurred or out of focus.
In very poor light and contrast, what is the camera actually focusing on? I would have expected it to hunt or fail to lock, not instantly decide and then give me frames where nothing looks sharp. Is this normal behavior for AI Servo, and how can I improve the results?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
3
"AI Servo mode" is the clue to the answer. In general across cameras I've used, the single shot focus mode will "give up" and refuse to take a picture — but in continuous or "servo" mode, the camera does its best to take an image of something when you hit the shutter, even if focus isn't right.
You say "Why a quick focus and then NOTHING in the shot in focus?", and the answer is that the camera thinks you've asked it to prioritize capturing a frame over accurate focus.
On some cameras, this behavior is adjustable, but I don't think it is on yours.
That means you should change to AF One Shot (AF-S on Nikon or Pentax). The camera might be slower and you might miss the exact moment, but at least it will be in focus.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
13y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — this can happen in AI Servo. In that mode, the camera generally prioritizes getting a frame when you press the shutter, even if focus is not fully confirmed. In low-contrast light, it may make its best guess rather than refusing to shoot, so you can get a quick “lock” but no truly sharp subject.
A few things can contribute:
- On the 1100D, only the center AF point is cross-type, so AF performance is limited in poor light/contrast.
- If the camera selected AF points automatically, it may have focused on something with more contrast than the bird.
- At 400mm, blur from shutter speed or vibration can also make shots look out of focus, even on a tripod.
To improve results:
- Manually select the center AF point.
- Use One Shot AF if the subject is not moving much; it is more likely to refuse focus than take a badly focused shot.
- Use a faster shutter speed to rule out motion blur and vibration.
- Check which AF point was actually used when reviewing the images.
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AI13y ago
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