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I'm trying to repair a Rebel T6 with a strange problem. All settings are stock, AF One Shot, center point selection. I've tested with 3 lenses including the 18-55 kit lens. After turning the camera on, it focuses quickly and accurately with the viewfinder, near and far, in all zoom ranges.

However, after taking a photo, it refuses to focus on anything - going back and forth in the focus range and never finding focus. It stays this way until I wait a while (5 minutes or so). Changing lenses, turning the camera off and on again, removing and replacing the battery, none seem to affect whether the camera will autofocus again.

Steps I've taken:

  • ensured the environment is well lit, focusing on high contrast subjects
  • cleaning lens and mount contacts
  • cleaning the mirror
  • cleaning the focus screen (last resort)

Live mode focus does work, but seems to take a long time (1-2 seconds) in making small adjustments to find focus. I haven't used a T6 before, but it seems like it should focus faster than this.

Any help would be appreciated. I'm comfortable with taking the camera apart to figure it out, this was a $50 eBay buy.

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    \$\begingroup\$ Behind the main mirror, there is a secondary mirror that reflects light toward the focus sensors on the "floor" of the camera (this is the "submirror" in these schematics). If that one is stuck or very slow to settle to its normal position this could explain your problem. \$\endgroup\$
    – xenoid
    Jun 16, 2019 at 23:24
  • \$\begingroup\$ Nice, I thought I had read about something down there having to do with focusing, but I couldn’t see how light would get there so I dismissed it. I’ll look into that and update later. \$\endgroup\$
    – Rakurai
    Jun 17, 2019 at 0:13

1 Answer 1

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Thanks to @xenoid , I checked out the secondary mirror and found that it wasn’t moving all the way into position after taking a photo, so the AF sensor wasn’t receiving the correct light. Closer inspection revealed a broken hinge on the secondary mirror, shown in the photo below. Looks like I’m taking this camera apart.

this photo

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