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05-15-2012, 12:58 PM   #1
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k-r weird mirror flop - more details

Some more details, more puzzles -
I've posted a video on
of the mirror flops.
The k-r is just back from repair for random uncontrolled flops "diaphragm mechanism replaced"
no flopping at all with fully auto lenses - only with manual, and "flop" rate varies from lens to lens
no flop with these lenses on the K100, but it turns out they have a different mechanism (the mirror doesn't cycle in optical preview)

On the "good" lenses the optical preview cycles the mirror on RELEASE of the green button (depress button steps down aperture, then mirror flop on release)
On the manual lenses (which is where you need the preview) depress button steps down aperture AND cycles mirror, and then cycles again on release
On some lenses it will also flop after the end of the video preview (i.e. couple of seconds after picture), on others will flop again when you switch it off.
Sometimes the mirror simply jams in the "up" position, and won't fall until powered off.

Because the K100 has a different mechanism, I can't really tell with this is a problem with the lenses or not - my old Pentax A and M lenses vary, the 50mm f2 seems OK, but the 135mm F3.5 sets it off now and again; worst offender is the Kiron 28mm F2 (pentax K mount), the Sigma 24mm F2.8 is close second. No problem at all with old M42 lenses, as they don't stop down and don't seem to trigger the "flop".

If it is the lenses, then it's a pain not to be able to use them reliably (when they worked fine on the K100) - I worry that this is a sign of some other problem with the mirror/aperture mechanism.

Any detectives out there who can work this out?? Much appreciated.

05-15-2012, 01:09 PM   #2
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Your kr needs to be repaired,simple as that.
05-15-2012, 01:18 PM   #3
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I think you may be right - just didn't want to be without it for another month . . . .
05-17-2012, 11:31 AM   #4
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I've done a bit more detective work: the lenses that are most problematic differ from the unproblematic ones in the way that the aperture levers move. I have a 35mm F3.5 manual - it's impossible to make it do the "flop". Two things: (i) The aperture lever is stiff (it works though). (ii) When it is fully open there is no play at all in the lever.

The lenses that are worst have very loose aperture levers, and, the very worst ones are ones that when the aperture is fully open, there is still play in the lever (the worst of all, the Kiron 28mm, has 100% play when fully open) an intermediate one (Pentax M 135mm) has some play. So, the amount of "flopping" seems to be proportaional to the looseness and the "play" in the aperture lever.

I don't know enough about the mechanism to now work out how the looseness and play would increase the chance of double flopping, but it seems to be too much of a coincidence not to be relevant. Any ideas?

09-27-2012, 07:24 PM   #5
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I was just shooting with my pentax 1:3.5 135mm manual lens on my K-r and I got the mirror flop too. It happens with the green button for metering and the shutter button. It mirror wouldn't come down until I had turned off the camera and removed the battery then turned it back on. My camera is out of warranty so I don't want to spend a fortune getting the camera checked/fixed if the aperture lever on the manual lenses are the issue. It doesn't happen with my kit lenses. I did notice the the lever on my 135mm moves up and down vertically where as the lever on the kit lenses move up and down and curve around lens.....wonder if that has anything to do with it?
09-28-2012, 01:25 AM   #6
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Hi, i'm not sure if it does. Mine has now been repaired twice (under warranty) with a replacement of the shutter/diaphragm unit. That has almost done the trick - it only "flop" on maybe one shot out of 200, rather than 1 out of 10. One "fix" you can try if it is out of warranty is to tape over the contacts on the problematic lens (if it is a manual non-"A" lens it doesn't make any difference anyway) - that seemed to work for most of mine (similarly, any m42 lenses whose body does not make contact (like a Helios 58mm) - no problem at all.

Worth a try.
09-28-2012, 08:12 AM   #7
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Unfortunately its all of my Manual lenses without contacts that cause the problem
10-27-2012, 03:07 PM   #8
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I was having that problem with the 100mm f/4 macro. Switched from the rechargeables to AA Lithiums in the accessory holder and the problems went away. I think it might have been a voltage sensitivity problem.

10-29-2012, 02:41 AM   #9
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Same problem for me (Kr with a summilux with bayonnet from leitax). Manual lense and the mirror flop more on some than others.
Not too sure about that but do you have the feeling that it vary depending on your aperture slected (on the lense).
speed. But Have a wider aperture and it stop fliping.

I have heard before that it can be a problem coming from the rechargeble battery as well.
Anyone can confirm it disapear after switching to AA lie FarFel53 ?

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