[bwDraco]

I've discovered a rare but potentially serious bug on my K-5. It can happen randomly, but can be consistently reproduced with a specific sequence of steps:

1. Partially dismount the lens (release and rotate it slightly but do not remove completely).
2. Turn the mode dial to the Movie position.
3. Start movie recording.
4. Fully mount the lens. The camera will detect a lens change and stop movie recording.

The camera then drops out of Live View and a continuous buzzing noise, possibly with some clicking, is audible. The camera locks up until the lens is dismounted (partially or completely) or the battery is removed.

The alarming part of this is that the area of the camera body closest to the diaphragm motor, the protrusion from the lens mount below the AF assist lamp near the main handgrip, can get hot if this is left unchecked. I'm afraid this behavior could damage the diaphragm control mechanism or overheat the diaphragm motor.

Is anyone else able to reproduce this behavior? Why might this be happening?

—DragonLord

---

Last edited by bwDraco; 06-23-2015 at 06:52 PM.

[Adam]

I think it happens if the drive shaft isn't properly engaged. Can sometimes happen after mounting a lens; wiggling it a bit seems to help.

[pentaxus]

I bet it's the focus motor like Adam said. I got that when I mounted my 18-55 with an extension tube. The contacts on the tube told the camera that the lens is AF and since I had the camera set to AF, the motor was trying to make focusing happen. Quite noisy.

[bwDraco]

Definitely not the in-body AF motor. It's the diaphragm motor, which is much quieter. If it were the AF motor, it would be the area near the AF switch that's getting hot, not the bulge below the AF assist lamp.

—DragonLord

[jbinpg]

One reason why I always turn off the camera power when changing lenses. Other reason is that charged sensor attracts dust.

[LoneWolf]

One reason why I always turn off the camera power when changing lenses. Other reason is that charged sensor attracts dust.

jpinpg is correct.

Advice (both written and unwritten) is that you should ALWAYS turn the camera off when changing lenses, changing cards, removing batteries or removing grip etc. It is much safer and avoids possible hardware problems or funnies or card or software corruption.