Mirror lockup malfunction - New type?

Started Jun 6, 2005 | Discussions thread
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Ben Seese
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Mirror lockup malfunction - New type?
Jun 6, 2005

I seem to have stumbled upon a new way for the D70 to break. At least, I haven't been able to track down any other posts here that describe it.

It's similar to the somewhat common "mirror lockup" error, in which the mirror fails to drop after an exposure, "ERR" shows on the screen, and pressing the shutter release a second time drops it back down. Here's the most recent post describing that:
http://forums.dpreview.com/forums/read.asp?forum=1034&message=13539276

In my case though, the mirror fails to rise during some exposures. I end up with the bottom part of the picture being nearly black. (Remember that the image is upside-down on the sensor, so the mirror blocking the top of the sensor results in the bottom of the image being black.)

The punch line is that yes, I am sending it in for service tomorrow. In the meantime, though, I'll lay out the details here. It started last night when I was on my covered porch shooting a lightning storm. My settings were:

kit lens @ 18mm
tripod mounted
manual exposure:
4 sec
f/8
ISO200
manual focus
continuous drive mode
RAW+Basic

I was holding the shutter release down with my finger (trying to hold very still), while it fired off shot after shot. Out of about 150 exposures, the malfunction happened on about 10.

Between exposures, instead of the normal crisp pop-pop sound of the mirror flapping down and back up, it would sound like pop-pop-plunk. I can't yet explain what the "plunk" sound is, but it always happens at the beginning of the exposure time, immediately after the normal "pop" of the mirror flapping up.

When it occurs, that one exposure is messed up, but the camera immediately returns to normal and will happily keep firing away. While I was shooting the lightning storm, I did hear the funny "plunk" sound happening, but didn't think anything of it until I got inside to review the pictures.

The messed up pictures turn out being very underexposed over the entire frame (in addition to the lower 1/4 to 1/2 being nearly black). In my testing today, I've determined that the aperture is closing down all the way, not just to the f/stop I have set on the camera. So for instance, if I have the aperture set to f/11 (with the kit lens zoomed out), and it happens, I can open the NEF in Capture and boost the exposure two stops, and the top half of the pic will match a shot in which it didn't happen (because the lens' minimum aperture is f/22, two stops smaller than it was supposed to be). Also, the dust spots on the sensor become much sharper than in the normal shots, which is a sure sign that the aperture is smaller.

Also, in the top half of the picture, sometimes there is a series of odd horizontal banding. No explanation here...

What I find somewhat (more) bizarre is that the blackened lower half is not quite black. In some of my lightning shots, I had some street lights in the foreground at the bottom edge of the frame, and in the messed up shots, they are visible, though very dark. MAYBE the mirror IS rising all the way, and the "plunk" sound is it falling halfway down...?

Today, I've been able to reproduce it using all three of my Nikkor lenses (18-70, 50mm 1.8, 70-300G). It happens for shutterspeeds as fast as 1/15 sec (haven't cared to try any faster). It happens for all apertures.

(cont'd below)

-Ben

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