Why does my Canon 1300D struggle to focus when I use ND filters?
Asked 4/16/2021
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When I mount ND8 or ND10 filters on my Canon 1300D kit lens, autofocus often won’t lock properly and manual focus also seems difficult. Without the filter, focusing is normal. With the filter on, the subject looks slightly blurry through both the viewfinder and Live View, even in bright daylight. If I focus first and then attach the filter without moving the focus ring, the image can still appear soft. Is this just because the ND filter reduces too much light for focusing, or could the filters themselves be causing blur?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
5
Camera focusing systems have a "Focusing brightness range" (Canon parlance), "detection range" (Nikon parlance) specification. This is found in the specifications section in your manual. Your camera is rated for 0-18EV for the center focus point, 1-18EV for the other focus points. Adding an ND filter will reduce the scene brightness below the threshold for reliable autofocus.
The usual solution is to lock focus with the filter off, add the filter and take the shot.
Originally by user98537. Source · Licensed CC BY-SA 4.0
user98537
5y ago
0
Generated from our catalog & community — verify before relying on it.
Two things could be happening.
First, ND filters reduce the light reaching the camera, and autofocus systems have a minimum brightness/contrast level they need to work reliably. On a Canon 1300D, a strong ND can push the scene below that threshold, so AF may hunt or fail. A common workaround is to focus without the filter, switch to manual focus, then attach the filter and shoot.
Second, if the image still looks soft even after you focus first and carefully add the filter without moving focus, the filter itself may be degrading the image. A good ND filter should darken the scene, not noticeably blur it. If every filter you try does this, inspect them for damage, dirt, haze, smearing, or poor optical quality.
So: if autofocus fails only because it gets too dark, focus first and then add the ND. If the image becomes blurry just by adding the filter, the filter is likely the problem.
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AI5y ago
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