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08-27-2017, 11:50 AM   #1
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K-30 with dawning Aperture problem - what about Pentax-F lenses?

Hi. Unfortunately my K30 is starting to show symptoms of the dreaded Aperture Problem. I have no spare money to ever fix it and will just need to live with it.
However as I've been so poor, the number of actual "new" lenses that I have is relatively small. I have a bunch of Pentax-M/M42 glass which obviously continue to work as before as they contain no automatics.

However, what about Pentax-F lenses? Do they continue to work relatively fine, with the only difference being that I need to adjust the aperture from the aperture ring on the lens itself, and not using the dial on the body? AF should work just fine, right?

So, with a AF-capable lens that has an aperture ring the only difference is that I'd "need" to use the ring and not via software from the body?


I can live with that. Actually I'd prefer adjusting the aperture from the ring in the first place, so that is really not bad if that's the case.


The only real problem then that is left is that I can't adjust aperture on my Sigma 10-20mm f/3.5. That is sad.

08-27-2017, 12:13 PM   #2
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Are you handy with electronics? An $8 solenoid seems to fix the problem.

08-27-2017, 12:13 PM   #3
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QuoteOriginally posted by AnttiV Quote
Hi. Unfortunately my K30 is starting to show symptoms of the dreaded Aperture Problem. I have no spare money to ever fix it and will just need to live with it.
However as I've been so poor, the number of actual "new" lenses that I have is relatively small. I have a bunch of Pentax-M/M42 glass which obviously continue to work as before as they contain no automatics.

However, what about Pentax-F lenses? Do they continue to work relatively fine, with the only difference being that I need to adjust the aperture from the aperture ring on the lens itself, and not using the dial on the body? AF should work just fine, right?

So, with a AF-capable lens that has an aperture ring the only difference is that I'd "need" to use the ring and not via software from the body?


I can live with that. Actually I'd prefer adjusting the aperture from the ring in the first place, so that is really not bad if that's the case.


The only real problem then that is left is that I can't adjust aperture on my Sigma 10-20mm f/3.5. That is sad.
To be able to change the aperture I believe you'd need a Takumar lens, which has an entirely manual diaphragm. If the aperture actuator fails, a K-mount lens would otherwise always shoot wide-open since the lever by default opens up the diaphragm.

Of course, if you cut off the aperture lever entirely (either in camera or on the lens), then lenses with an aperture ring would work as you're describing (and just like Takumars in the sense that the diaphragm would be manual). But rather than butchering gear, I think you'd be better off with the DIY fix.

Adam
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08-27-2017, 12:24 PM   #4
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QuoteOriginally posted by Adam Quote
To be able to change the aperture I believe you'd need a Takumar lens, which has an entirely manual diaphragm. If the aperture actuator fails, a K-mount lens would otherwise always shoot wide-open since the lever by default opens up the diaphragm.

Of course, if you cut off the aperture lever entirely (either in camera or on the lens), then lenses with an aperture ring would work as you're describing (and just like Takumars in the sense that the diaphragm would be manual). But rather than butchering gear, I think you'd be better off with the DIY fix.
Why would it shoot wide open, if the lens has an aperture ring? I can manually dial down the aperture to what I want from the ring, the camera won't open it up if the ring is not in the A-position?

Actually, that is even one of the proposed test to see if certain unit has the aperture block problem or not (to check if the exposure is correct by dialing the ring rather than in the A-position, I just read from a sticky). So it really should work with F lenses even if the block fails. That's really good news.



---------- Post added 08-27-17 at 10:26 PM ----------

QuoteOriginally posted by clackers Quote
Are you handy with electronics? An $8 solenoid seems to fix the problem.
And probably just filing the horse-shoe inside the actuator itself. It just looks like something I don't want to do without having a spare body, at least in the case if it would still work with F-lenses.

While I'm OK with electronics, I'm also 10/10 proficient in dropping stuff and making mistakes

08-27-2017, 12:29 PM   #5
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QuoteOriginally posted by AnttiV Quote
Why would it shoot wide open, if the lens has an aperture ring? I can manually dial down the aperture to what I want from the ring, the camera won't open it up if the ring is not in the A-position?
Because the aperture ring limits the smallest possible aperture, but the aperture lever defaults to wide-open and will keep the lens there until the actuator moves it down to achieve the aperture set on the aperture ring. This is how open-aperture metering is implemented on Pentax cameras. If it worked the way you're describing, the viewfinder would get darker as you move the aperture ring.

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08-27-2017, 12:29 PM   #6
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QuoteOriginally posted by AnttiV Quote
Why would it shoot wide open, if the lens has an aperture ring? I can manually dial down the aperture to what I want from the ring, the camera won't open it up if the ring is not in the A-position?
On K-mount lenses (unlike m42 on k-mount) the aperture is wide open during focusing and only closes when the shutter button is pressed. You set the aperture you want on the aperture ring, but nothing happens until the image is taken. This is by design so that you or the AF mechanism can focus with full light not stopped down which causes the viewfinder to be very dark.
08-27-2017, 12:31 PM   #7
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If this ever happens to my K30 I'd definitely try filing the horse shoe thingy as shown in a video tutorial, and if that didn't work, probably tear out whatever is in the camera body that contacts the lens aperture lever before I would risk crippling all my lenses.
08-27-2017, 12:37 PM   #8
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QuoteOriginally posted by Adam Quote
Because the aperture ring limits the smallest possible aperture, but the aperture lever defaults to wide-open and will keep the lens there until the actuator moves it down to achieve the aperture set on the aperture ring. This is how open-aperture metering is implemented on Pentax cameras. If it worked the way you're describing, the viewfinder would get darker as you move the aperture ring.
That doesn't make ANY sense. As in when the aperture block fails, the exposures become DARK, not light. This would not be such a problem if after the failure you could only use lenses with their WIDEST aperture, but unfortunately it's the other way around. If the block fails in a K30/K50 the resulting exposures will always be dark, hence why it is also called "Dark Frame problem".

---------- Post added 08-27-17 at 10:39 PM ----------

QuoteOriginally posted by jatrax Quote
On K-mount lenses (unlike m42 on k-mount) the aperture is wide open during focusing and only closes when the shutter button is pressed. You set the aperture you want on the aperture ring, but nothing happens until the image is taken. This is by design so that you or the AF mechanism can focus with full light not stopped down which causes the viewfinder to be very dark.
Yes, I know. But the problem is not that the aperture gets stuck in "open" position, the problem is that if it fails, every exposure will be dark after that. It behaves like you'd have selected the smallest aperture possible on the lens, not largest.

---------- Post added 08-27-17 at 10:42 PM ----------

You'll have to remember that it is not the actual aperture *motor* that fails, but the aperture "block", the one that "locks in" the desired aperture (like said, it's just a simple solenoid, not a motor or anything fancier). What happens is that there's a part that travels magnetically and when it fails, it gets "stuck" to one position. Maybe that position is "select smallest aperture possible", or something like that. I don't know.

08-27-2017, 04:11 PM   #9
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Long and the short - it's failing. Go Takumar or go home. Your instincts on that one are spot on, OP.

When it finally, irrevocably fails, you can report based on experience exactly what the M and F series lenses do when you use the aperture ring. Experimental evidence trumps theory always.
08-27-2017, 07:04 PM   #10
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It's my understanding when in the failure mode the aperture lever on the camera body will always move to the full stop down position. Normally the lever would move as far to stop the lens down to the set aperture. This is why the images come out most of the time greatly underexposed. When using the aperture ring on a lens the iris will stop down as far as set on the ring. The aperture will only stop down in "M" mode when not set in the A mode or non-A lenses.
08-28-2017, 01:02 AM   #11
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QuoteOriginally posted by Not a Number Quote
It's my understanding when in the failure mode the aperture lever on the camera body will always move to the full stop down position. Normally the lever would move as far to stop the lens down to the set aperture. This is why the images come out most of the time greatly underexposed. When using the aperture ring on a lens the iris will stop down as far as set on the ring. The aperture will only stop down in "M" mode when not set in the A mode or non-A lenses.
This is my understanding also. Well we'll see once the last of the life of the aperture block fails. I'll report back here what works and what doesn't when that happens. Meanwhile I'm not that scared anymore, since I believe I can still use *some* of my lenses, but unfortunately I can't rely on this camera anymore. I can't trust it to make correct exposures when it's failing.

I'm also quite deeply (compared to my income) invested in Pentax, so right out switching brands is quite out of the question... so another used Pentax body it is... I hope I can find a good deal on a K3/K3ii.
08-28-2017, 03:45 AM   #12
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It's been said, but for clarity you will not be able to use a K, M, A, F or FA type lens with a failed camera. These are all auto-aperture lenses and need the camera coupling to stop down. Turning the aperture ring will have no effect. The earlier Takumar types, plus equivalent third party options such as the Tamron Adaptals from the 1970s, with auto/manual aperture switches, will work as the aperture will stop down manually before the shot.

Last edited by mcgregni; 08-28-2017 at 10:49 AM.
08-28-2017, 04:08 AM   #13
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QuoteOriginally posted by mcgregni Quote
It's been said, but for clarity you will not be able to use a K, M, A, F or FA type lens with a failed camera. These are all auto-aperture lenses and need the camera coupling to stop down. Turning the aperture ring will have no effect. The earlier Takumar types, plus equivalent third party options such as the Tamron Adaptals from the 17970s, with auto/manual aperture switches, will work as the aperture will stop down manually before the shot.
Have you tested it? I find it hard to believe, since when the block fails, all exposures are DARK, so the camera will *definitely* stop down everything, that's the whole problem. Also on this site there is a sticky that I now fail to find that explains a few procedures how to be sure if the block has failed. One of these procedures is to test it with a lens that has an aperture ring, first in A-mode than then stopped down manually. The post says that it should work if the ring is not in A-position.

Also there's at least one person that I just bumped into in a thread saying they WILL work:
Is there an emergency work-around for the aperture motor failure on the K-50? - PentaxForums.com
08-28-2017, 04:47 AM   #14
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I think the part that you're failing to appreciate is the technology inside the lenses and how the camera controls them. For whatever reason, if a camera cannot control and stop down the aperture on those lenses correctly, then there is no way to control the exposures. Whether the aperture ring is set to the A position or not makes absolutely no difference.

I've not experienced aperture motor / block failure, but an understanding of the lens tech and the theory is enough to appreciate what is.possible and not possible.
08-28-2017, 06:32 AM - 1 Like   #15
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QuoteOriginally posted by mcgregni Quote
It's been said, but for clarity you will not be able to use a K, M, A, F or FA type lens with a failed camera.
Why this miss information keeps on spreading here? I have been shooting almost a year now with M series lenses on my k30 after the ABF. Camera works perfectly fine in manual mode. You can adjust aperture with green button and you can shoot with CIF.

I don't own any of the A, F or FA lenses, so can't personally test and confirm it, but cannot see why they would not also work on manual mode.
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