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09-07-2014, 11:46 AM   #1
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Mirror flap Data

I have mounted the following manual lenses on my k-r over the last couple of years:

Soligor 28mm f/2.5: always mirror flap
Chinon 45mm f/2.8: always mirror flap
Revuenon 50mm f/1.4: never mirror flap, even if I try to induce it
Chinon 50mm f/1.9: never mirror flap, even if I try to induce it
Pentax 55mm f/1.8: never mirror flap, even if I try to induce it
Ricoh 55mm f/2.2: never mirror flap, even if I try to induce it
Helios 58mm f/2.0: never mirror flap, even if I try to induce it

When does the mirror flap with the two lenses?
(i) When the batteries are low (hypothesis only)
(ii) switching liveview off (hypothesis only)
(iii) Turning the aperture ring (confirmed)
(iv) half-pressing the shutter button (confirmed)

All of these lenses are fully manual, and the mount is identically shaped on all of them, then why why does the flapping occur in the cases of 28mm f/2.5 and 45mm 2.8 only?

Could it have to do with the amount of light the lens lets in? There is no mirror flap in the case of the relatively fast lenses.

I have seen reported instances of mirror flap on the following models; the causes of the flapping may vary:
kx
kr
k5
k30
k50
k500
k3

I have seen no reported instances of mirror flap on the following models:
k7
k5ii
k5iis

It would appear that the mirror flap disease was introduced to the Pentax line-up with the kx.

What do we know about this issue with absolute certainty? I know that it has already been discussed a lot, but I am yet to come across conclusive evidence as to its cause(s).


Last edited by DominicVII; 09-07-2014 at 12:13 PM.
09-07-2014, 03:12 PM   #2
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Dominic could you please specify the mount on these lenses: M42/Normal K/t-mount or other painted mount
And you might have a look at my piece:
https://www.pentaxforums.com/forums/116-pentax-k-r/271872-tests-plated-vs-pai...r-whats-t.html
09-07-2014, 03:15 PM   #3
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If they are K mount it can be the aperture lever is not allowing the camera lever to return to it's stop point or the aperture spring on the lens is too strong
that happened with my adaptall lenses. Upsets the timing between the shutter and mirror.
If they are M42 it could be the way the contacts are shorted by the lens mount.
09-07-2014, 03:25 PM   #4
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QuoteOriginally posted by marcusBMG Quote
Dominic could you please specify the mount on these lenses: M42/Normal K/t-mount or other painted mount
And you might have a look at my piece:
https://www.pentaxforums.com/forums/116-pentax-k-r/271872-tests-plated-vs-pai...r-whats-t.html
Here are the two culprit lenses - both K-mount. I have been observing this issue for quite some time now, and sometimes it appears to be a metering issue. You press the green button in M mode to meter, whereas in Av mode the camera seems to be repeating this procedure like a lunatic.

ANNEX: My opera browser and PF don't seem to get along; the picture upload failed.


Last edited by DominicVII; 09-07-2014 at 03:39 PM.
09-07-2014, 03:45 PM   #5
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Ok, the uploads succeeded this time; my lack of patience was the problem, not the Opera browser. Let me know if you see anything peculiar about these lenses that makes my camera go gaga.

EDIT: that second picture was uploaded in error.

---------- Post added 09-08-14 at 00:55 ----------

QuoteOriginally posted by bobpur Quote
If they are K mount it can be the aperture lever is not allowing the camera lever to return to it's stop point or the aperture spring on the lens is too strong
that happened with my adaptall lenses. Upsets the timing between the shutter and mirror.
If they are M42 it could be the way the contacts are shorted by the lens mount.
I would not rule out the possibility that you are indeed right. But the aperture springs on both lenses are as they should be. I recently compared the springs on all my lenses; no anomalies discovered.

Others here have pointed out that these problems only occur with lower end cameras, and not with the flagship models. Again, I am in no position to assess the validity of this claim. But it is interesting to note that no such issues were reported with the k7.
Attached Images
View Picture EXIF
PENTAX K-r  Photo 
View Picture EXIF
PENTAX K-r  Photo 

Last edited by DominicVII; 09-07-2014 at 03:56 PM.
09-07-2014, 04:07 PM   #6
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Those mounts look completely normal.

I am particularly intrigued by the absence of flopping with the helios, which I presume is M42. I have never had flopping with my (origina)l K-r actually with a standard P-KM mount lens.The lens I was using today - PKM mount Kiron 28mm - case in point, regardless of mode. It's always been with M42's and t-mounts, though since I currently have 3 K-r bodies (long story) I'll get some lenses out and do a bit of a survey.
Have you tried the foil trick I mention in my piece? i would be interested to hear how that goes.

Last edited by marcusBMG; 09-07-2014 at 04:12 PM.
09-07-2014, 04:15 PM   #7
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QuoteOriginally posted by marcusBMG Quote
Those mounts look completely normal.

I am particularly intrigued by the absence of flopping with the helios, which I presume is M42. I have never had flopping with my (origina)l K-r actually with a standard P-KM mount lens. It's always been with M42's and t-mounts, though since I currently have 3 K-r bodies (long story) I'll get some lenses out and do a bit of a survey.
Have you tried the foil trick I mention in my piece? i would be interested to hear how that goes.
I have a K-mount version of the Helios.

I found your piece extremely informative. Well done. But I will have to reread it, so as to determine with certainty just what it is that is applicable to K-mount lenses.

I really hope that this issue will have disappeared forever with coming of the K-S1:
09-07-2014, 04:46 PM   #8
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I'm beginning to think that there is no single reason that any of us will discover; it may just be that a piece of sophisticated equipment such as a modern-day DSLR will exhibit a problem under some type of duress. This duress may be merely the result of one of more design elements falling outside of "nominal". In this circumstance any delicate part of the equipment will act up. In our case, it's the mirror assembly, which could very well be one of the most sensitive (and temperamental, it seems) parts of the beast.

Not having been anything other than a Pentaxian I will reserve judgement against Pentax, Hoya or Ricoh. Although I've not delved deeply into complaints towards any other brand, I have run across some similar incidences therein.

Beyond my speculation I have experienced Mirror Flop on my K5, but mostly when the battery is newly charged. My solution is to use Live View for a few minutes and it usually goes away. Annoying, I know, but manageable nonetheless.

Jeff

09-07-2014, 06:04 PM   #9
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QuoteOriginally posted by jamarley Quote
I'm beginning to think that there is no single reason that any of us will discover; it may just be that a piece of sophisticated equipment such as a modern-day DSLR will exhibit a problem under some type of duress. This duress may be merely the result of one of more design elements falling outside of "nominal". In this circumstance any delicate part of the equipment will act up. In our case, it's the mirror assembly, which could very well be one of the most sensitive (and temperamental, it seems) parts of the beast.

Not having been anything other than a Pentaxian I will reserve judgement against Pentax, Hoya or Ricoh. Although I've not delved deeply into complaints towards any other brand, I have run across some similar incidences therein.

Beyond my speculation I have experienced Mirror Flop on my K5, but mostly when the battery is newly charged. My solution is to use Live View for a few minutes and it usually goes away. Annoying, I know, but manageable nonetheless.

Jeff
I am also inclined to believe that more than one cause is at work here. But that doesn't help me much: my main reason for choosing Pentax was precisely that I could shoot with old glass without recourse to adapters.
09-07-2014, 09:09 PM   #10
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Dominic, could you please perform the null test for us? In other words, could you please try performing your test with no lens?

In my case, lenses with no contacts (and the lens-less test) were the worst offenders.
09-08-2014, 04:05 AM   #11
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QuoteOriginally posted by ofer4 Quote
Dominic, could you please perform the null test for us? In other words, could you please try performing your test with no lens?

In my case, lenses with no contacts (and the lens-less test) were the worst offenders.
Test without lens performed five times:

going in and out of liveview, taking pictures, half-pressing shutter release, pressing random buttons.

No symptoms of mirror flap without a lens.
09-08-2014, 06:36 AM   #12
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QuoteOriginally posted by DominicVII Quote
I have a K-mount version of the Helios.
Ok in that case its just the same as the other lenses.


QuoteQuote:
I found your piece extremely informative. Well done.
Thank you

QuoteQuote:
But I will have to reread it, so as to determine with certainty just what it is that is applicable to K-mount lenses.
Its about 1. the exposure errors inherent in using non KAF/KAF2 lenses on pentax dslr; 2. the additional glitches due to non contactivity of black painted/anodised mounts.
For more on #1 see Lowell Goudges' graph.

QuoteQuote:
I really hope that this issue will have disappeared forever with coming of the K-S1:
You should be so lucky! personally I am pretty sure that the problems reside in the firmware - the computer code that operates the camera.Our collective inability to track down a consistently credible mechanical or logical cause is symptomatic....
09-14-2014, 03:56 PM   #13
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More flopping!

I just had a bad experience with a PKA adaptall mount.

I was checking out a couple of mounts recently acquired. One of my old mounts I had marked as faulty. I couldn't remember why so I put it on the K-r with a lens to check. Bad move!!
The exposures on a couple of tests were off. Then the camera started flopping! Bad flopping. The "everything you touch causes repeated flop" flopping. Turned off, took out the battery, no change.

Then I tried to take the lens off. Something was sticking. Uh Oh!. Because its an adaptall I was able to leave the mount on and detach the lens and have a look see.
After some careful scrutiny I realised the aperture lever was misaligned: had slid almost past the actuation lever in the camera, in fact was jammed against it. Mirror and lever had not quite returned to rest positions.

I was able to cut away the plastic lever guard on the mount and then use an angled toothpick to hook the aperture lever and free it up. Mount then came off normally. With relief, camera is OK.
Mount has a slightly bent aperture lever (plus I suspect internal electronic issues).

But I wonder if perhaps something is just slightly out of kilter on your two lenses Dominic , not enough to cause an actual problem, but just enough to make the camera think there is...??
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