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12-06-2011, 08:51 PM   #1
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lens flop on kx?

I have had the camera about a year, part of why i chose pentax was some old hand me down glass. I have been using it nearly a year with the green button for metering. I would push the green button, hear the mirror "flop" and watch as shutter speed changed. Never really thought twice about it, thought it was the norm. Fast forward to yesterday. I get my m42-k adapter and throw on an old s-m-c tak and when i push the green button. At first I thought metering wasnt working at all, then i realized that it was. AFter a brief search it turns out that the "flop" I am hearing with my other lenses is not supposed to happen. What should I do about this? What is the fix?

12-06-2011, 09:00 PM   #2
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That's just how it works with manual lenses. After it stops down the lens it cycles the mirror. This is a holdover from the K2000/K-m. It doesn't do it with M42 lenses because it doesn't stop down the aperture. As far as the camera is concerned there is no lens on the camera when you are using an M42 lens.
12-06-2011, 09:01 PM   #3
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What you're referring to is stop-down metering. Generally it should only happen when the camera doesn't receive aperture info from the lens, i.e. when using M, K, or M42 lenses.

Are you seeing an F-- indication from your auto lenses?

https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html

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12-06-2011, 10:54 PM   #4
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The mirror doesn't "flop" or "cycle" when the green button is pressed while in M mode, it's the camera trying to actuate the aperture lever to momentarily close the diaphragm to the user set aperture. Set the camera to M mode, take the lens off the camera and press the green button to see for yourself, it's a completely normal function of the camera when shooting with KM type lenses.

12-07-2011, 12:49 AM   #5
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QuoteOriginally posted by excanonfd Quote
The mirror doesn't "flop" or "cycle" when the green button is pressed while in M mode
It can, when the contacts are improperly insulated/shorted, and it definitely is a malfunction. One of my old 135mm presets does this, unless I use an insulator around the base of the lens, like a piece of paper cut to form a washer. I've thought about painting the base of the lens, but decided to hold off until I find a type of paint that I'm fully confident won't chip over time and get into the mirror box.

Here's the thread I posted when I originally came across the issue: https://www.pentaxforums.com/forums/general-technical-troubleshooting/159200-...-m42-lens.html
12-07-2011, 03:07 AM   #6
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QuoteOriginally posted by Philoslothical Quote
It can, when the contacts are improperly insulated/shorted, and it definitely is a malfunction. One of my old 135mm presets does this, unless I use an insulator around the base of the lens, like a piece of paper cut to form a washer. I've thought about painting the base of the lens, but decided to hold off until I find a type of paint that I'm fully confident won't chip over time and get into the mirror box.

Here's the thread I posted when I originally came across the issue: https://www.pentaxforums.com/forums/general-technical-troubleshooting/159200-...-m42-lens.html
After reading your post in the redirected link, I tried to duplicate your result or what you call a malfunction with my K20D. My Jupiter 37A with infinity type m42 adapter on the lens doesn't cause a mirror flop, 37A exposes the contacts on the body like your Accura but the base is black so that might prevent the malfunction from occurring. I have tried a non-infinity m42 adapter (black anodized aluminum) and a chromed non-infinity m42 adapter - no mirror flop. Perhaps K20D isn't susceptible to this malfunction...

If you look through the viewfinder with your Accura lens (no insulating paper) while pressing the green button in M mode, the viewfinder should black out momentarily, correct? Pressing the green button in the M mode with an M lens mounted on the camera, causes the viewfinder to darken momentarily but not completely black out, even if the aperture is set to f22.
12-07-2011, 06:04 AM   #7
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QuoteOriginally posted by excanonfd Quote
The mirror doesn't "flop" or "cycle" when the green button is pressed while in M mode, it's the camera trying to actuate the aperture lever to momentarily close the diaphragm to the user set aperture. Set the camera to M mode, take the lens off the camera and press the green button to see for yourself, it's a completely normal function of the camera when shooting with KM type lenses.
If you take the lens off the camera it doesn't do anything when you press the green button. In M mode with a KM lens the aperture will stop down and the viewfinder will dim. The viewfinder will then black out when the mirror cycles.

BTW, you don't have to use the Green Button on a K-x in manual mode. The AV+- button will stop the lens down, another holdover from the K2000/K-m. This lets you set the Green Button to something useful, like optical preview.
12-07-2011, 06:16 AM   #8
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QuoteOriginally posted by Philoslothical Quote
It can, when the contacts are improperly insulated/shorted, and it definitely is a malfunction. One of my old 135mm presets does this, unless I use an insulator around the base of the lens, like a piece of paper cut to form a washer. I've thought about painting the base of the lens, but decided to hold off until I find a type of paint that I'm fully confident won't chip over time and get into the mirror box.

Here's the thread I posted when I originally came across the issue: https://www.pentaxforums.com/forums/general-technical-troubleshooting/159200-...-m42-lens.html
So how would I tell the difference between stopping down the apperature for metering or the mirror flopping improperly? It is the thread that you linked there that brought out this issue to me, before that I thought it was normal!!

QuoteOriginally posted by excanonfd Quote
The mirror doesn't "flop" or "cycle" when the green button is pressed while in M mode, it's the camera trying to actuate the aperture lever to momentarily close the diaphragm to the user set aperture. Set the camera to M mode, take the lens off the camera and press the green button to see for yourself, it's a completely normal function of the camera when shooting with KM type lenses.
Totally makes sense, is the viewfinder supposed to totally black out while doing it though (not just get dark as though its stepped down)?

QuoteOriginally posted by boriscleto Quote
If you take the lens off the camera it doesn't do anything when you press the green button. In M mode with a KM lens the aperture will stop down and the viewfinder will dim. The viewfinder will then black out when the mirror cycles.

BTW, you don't have to use the Green Button on a K-x in manual mode. The AV+- button will stop the lens down, another holdover from the K2000/K-m. This lets you set the Green Button to something useful, like optical preview.
Interesting... I have NEVER read that anywhere. Just tested it though and I just learned something new!!

12-07-2011, 06:58 AM   #9
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QuoteOriginally posted by boriscleto Quote
If you take the lens off the camera it doesn't do anything when you press the green button. In M mode with a KM lens the aperture will stop down and the viewfinder will dim. The viewfinder will then black out when the mirror cycles.
I have a M50/1.7 and a M120/2.8 and have never noticed the mirror flop with either; cameras used with these lenses are K100D and K5.
I've just tested the M120/2.8 on the K5 and paid attention to what is happening (at f/4, M mode) and it only dims the viewfinder when pressing the green button; it does NOT go black and there is no additional sound. The M120 has a silver base and shorts all contacts.

So it either depends on the lens or on the body.

QuoteOriginally posted by hawk232 Quote
So how would I tell the difference between stopping down the apperature for metering or the mirror flopping improperly?
Use a wide aperture (e.g. the widest) and press the green button while looking in the viewfinder. You will see it go a little darker (if you don't use wide open). If it goes totally black, it's the mirror.

hawk232, which lenses are you using? And which ones show the behaviour?
12-07-2011, 12:50 PM   #10
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QuoteOriginally posted by boriscleto Quote
If you take the lens off the camera it doesn't do anything when you press the green button. In M mode with a KM lens the aperture will stop down and the viewfinder will dim. The viewfinder will then black out when the mirror cycles.
If you take the lens off and look inside the camera, below red lens indexing dot there is the aperture lever actuating knuckle (don't know the exact term), pressing the green button while in M mode, the knuckle will move up and down while making 'snic, snic' sound. This action will take place whether the lens is attached or not because it's the camera that sets the mode. The only time the mirror should cycle is when you press the shutter release button, pressing and releasing the green button should not cycle the mirror. Which of your M series lenses do this?
12-07-2011, 12:59 PM   #11
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The aperture sound is pretty quiet, the mirror is loud. There is no mistaking the two. But since you have a K-x, there is also no separating them. The K-x, for some unknown reason, always flips the mirror when doing stop down metering. Most models don't do that, so indeed, all you'd hear is the soft swoosh of the aperture stopping down, but the K-x gives you a very loud clunk.
12-07-2011, 01:10 PM   #12
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QuoteOriginally posted by hawk232 Quote
Totally makes sense, is the viewfinder supposed to totally black out while doing it though (not just get dark as though its stepped down)?
The viewfinder will darken momentarily when the green button actuates the aperture lever, if the viewfinder is blacking out then it's a malfunction. I hope you are not encountering this problem, if so, can you state which lens(es) you are having this particular problem with and what body you shoot with?
12-07-2011, 01:21 PM   #13
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QuoteOriginally posted by excanonfd Quote
but the base is black so that might prevent the malfunction from occurring.
Right, it doesn't happen when the base of the lens is insulated from the contacts. Painted/anodized or plastic lens mounts won't cause it.

QuoteOriginally posted by hawk232 Quote
So how would I tell the difference between stopping down the apperature for metering or the mirror flopping improperly?
Stopping down the aperture doesn't totally obscure your view through the viewfinder. It doesn't cause it to go totally black, like when taking a shot. The mirror flop is also MUCH louder than the aperture mechanism, at least on my K-r. When it's metering properly, I can hardly hear anything from it.
12-07-2011, 02:13 PM   #14
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all tests performed on a kx body running ver 1.00 it was purchased dec of last year.

s-m-c takumar 50/1.4 with a pentax adapter f/1.4= no noise, no difference in viewfinder, shutter speed changes appropritly. f/16 no noise, or difference in viewfinder, shutter speed changes appropriatly

smc pentax m 50/2 f/2= whoosh noise, viewfinder VERY briefly goes black then back to normal. f/22= whoosh noise, viewfinder dims, does NOT go black

osawa 80-205/4.5 exact same results as "m" 50mm both opened up and stopped down

sakar 28/2.8 exact same results as "m" 50mm both opened up and stopped down

so it appears as though i am mistaken. when stopped down the screen only dims... what is the brief blackout wide open though??
12-07-2011, 02:29 PM   #15
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QuoteOriginally posted by excanonfd Quote
If you take the lens off and look inside the camera, below red lens indexing dot there is the aperture lever actuating knuckle (don't know the exact term), pressing the green button while in M mode, the knuckle will move up and down while making 'snic, snic' sound. This action will take place whether the lens is attached or not because it's the camera that sets the mode. The only time the mirror should cycle is when you press the shutter release button, pressing and releasing the green button should not cycle the mirror. Which of your M series lenses do this?
If you take the lens off the K-x it does nothing when you press the green button. If there is no KM lens on the camera it does not stop down. When using an M42 lens with a K-x the lens is reported as M42 or No lens in EXIF. Other Pentax cameras may operate differently but the K-x inherited this behavior from the K-m. With a KM lens on the camera it stops down and then the mirror flips. It is quite clear when you press the button. The viewfinder dims then turns black for a fraction of a second.

I have been using the K-x since Dec of 2009, it has always behaved this way.
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