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09-20-2015, 05:34 PM   #1
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K-50 Help - Metering is leading to pitch black photos

Howdy folks!

I took my camera out today for some photo-making after a month or so. I took a photograph in aperture priority mode and it came out almost pitch black. It seemed to be metering correctly through the OVF - so a bright day should have been fine with f/8.0 at 1/100s shutter speed, with an ISO of 400-800.

Note - this issue occurred both with my 18-55 and my 55-200.

I was able to get photos to come out via live view, but I had to bump the ISO way high, keep the lens wide open, and slow the shutter. This seems to indicate a sensor metering issue, but I don't know where to start. My google-fu is weak on this issue.

Thoughts? What questions should I be asking?

I'll upload some photos later with examples of what's going on.

09-20-2015, 05:43 PM   #2
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QuoteOriginally posted by newarchivist Quote
but I had to bump the ISO way high, keep the lens wide open, and slow the shutter. This seems to indicate a sensor metering issue,
If the scene is dark (with little light), lens wide-open, slow shutter and ISO high... that's normal to me. I don't know what is the metering issue there. Perhaps you can show us the photo to see if there is something you can do about it.
09-20-2015, 05:47 PM   #3
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QuoteOriginally posted by aleonx3 Quote
If the scene is dark (with little light), lens wide-open, slow shutter and ISO high... that's normal to me. I don't know what is the metering issue there. Perhaps you can show us the photo to see if there is something you can do about it.
Sorry I wasn't clear. It was broad daylight, so I shouldn't need to have a super slow shutter, high ISO, or a wide aperture. I'm cooking dinner at the moment; when I return from that I'll get a couple photos up.
09-20-2015, 05:52 PM   #4
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Could be an issue with the lens's aperture, or, more likely, the camera's shutter. Let's see the pics- just attach them straight out of camera.


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09-20-2015, 06:01 PM   #5
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QuoteOriginally posted by newarchivist Quote
Sorry I wasn't clear. It was broad daylight, so I shouldn't need to have a super slow shutter, high ISO, or a wide aperture. I'm cooking dinner at the moment; when I return from that I'll get a couple photos up.
In that case, as Adam suggested, it could be a problem with the lens/camera aperture mechanism or the camera's shutter. Remove the lens from the camera and check the lens aperture linkage to see if it moves smoothly.
09-20-2015, 06:21 PM   #6
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How do I check the lens aperture ring?

Here are the photos: https://www.flickr.com/photos/newarchivist/albums/72157656555887404 They were taken around 4pm today in Boston, facing southwest, with the sun in that general direction.
09-20-2015, 07:36 PM   #7
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The aperture ring should be closest to the camera body. It should be set to A or if you twist the ring, as far right as it can be set. You should notice that though if your looking at the back of the camera when your looking at the settings. My suggestion would be try full auto and see what that gets you vs your own settings. I've gotten mine so far out of whack that resetting the whole camera back to the defaults solved my problems.
09-20-2015, 08:21 PM   #8
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OP is using 18-55, and 50-200. They don't have an aperture ring.

Do you have access to a manual lens?

09-21-2015, 09:15 AM   #9
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Your metering mode is set to spot. Change it to matrix and see what happens.
09-21-2015, 04:44 PM   #10
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QuoteOriginally posted by Adam Quote
Could be an issue with the lens's aperture, or, more likely, the camera's shutter. Let's see the pics- just attach them straight out of camera.
QuoteOriginally posted by aleonx3 Quote
In that case, as Adam suggested, it could be a problem with the lens/camera aperture mechanism or the camera's shutter. Remove the lens from the camera and check the lens aperture linkage to see if it moves smoothly.
Here are the results of a test with both my 50mm f/2 (a 30 year old lens) and with the 18-55 kit lens: https://www.flickr.com/photos/newarchivist/albums/72157658522799428

It's not a spot metering issue, I don't believe. a) this test was run with matrix metering and b) the first album contains photos that were made with both spot and matrix. In auto mode, it seems to give a "good" metering value but then results in a way underexposed photo.

With the above test, I tried to keep the variables in this test down to shutter and aperture, keeping ISO at constant. I also kept the K-50 in matrix metering with the kit lens. I think it automatically goes to spot with the old manual lens(?). A few potentials quirks. First was that the kit lens shots were made at 35mm and the prime lens, of course, at 50mm. Secondly, I shot the photos in RAW and then had the camera convert them to JPEG. Finally, I was only able to get to f/22 on the prime, while at 35mm the kit lens was able to drop to f/29. Still, I think the evidence is clear that the aperture portal is not responding properly.

As aleonx3 and Adam noted, this is likely an aperture drive mechanism issue. After a lot of searching today, this seems to be a common K-30 and K-50 issue. Do any of you all know if Pentax/Ricoh have addressed this in any form? Other than a service request, do you all have suggestions?

Thank you all!

//edit: I am now seeing several threads from the past few days regarding similar issues in K-50s, K-30s, and K-500s. Damn.
09-21-2015, 09:39 PM   #11
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Your lens is closing down to f/22. Set the camera to manual focus, Av mode at f/5.6 or something, and start cycling the shutter. Every so often you'll see the lens close down to f/22 for no apparent reason. If that happens then you have a problem with your aperture arm motor mechanism.
09-22-2015, 06:11 AM   #12
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QuoteOriginally posted by 6BQ5 Quote
Your lens is closing down to f/22. Set the camera to manual focus, Av mode at f/5.6 or something, and start cycling the shutter. Every so often you'll see the lens close down to f/22 for no apparent reason. If that happens then you have a problem with your aperture arm motor mechanism.
I'm curious - how is this different than the test above? I was able to show that the exposure was the same at f/4 and f/29, essentially.
09-22-2015, 11:30 AM   #13
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QuoteOriginally posted by newarchivist Quote
I was able to show that the exposure was the same at f/4 and f/29, essentially.
I see what your saying with the samples, that is strange considering everything else is the same (iso, shutter speed) but exposure is nearly identical. I'm curious if those two samples are actually f4 and f29 respectively or the exif is inaccurate? Sorry, that doesn't really address your original issue, though. As for testing random aperture behavior as suggested by 6BQ5, I guess you can try mounting the camera on a tripod, 2-second timer and take a "camera-selfie" in front of a mirror? If that works the way I think it should you'd be able to see how big the actual iris is per shot. You may not be able to tell exactly what aperture it was but I can imagine the difference between f4 and f29 would be significant, then compare it to what the exif says - just a thought?

Also, your exif shows the camera is still running firmware 1.0, have you considered upgrading to the latest version (1.02)?
09-22-2015, 12:43 PM   #14
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QuoteOriginally posted by newarchivist Quote
I'm curious - how is this different than the test above? I was able to show that the exposure was the same at f/4 and f/29, essentially.
Just so you can see what the aperture blades are doing. That's all. Just snap away. The pictures you will take with your camera and store on the SD card are already paid for so start clicking.
10-05-2015, 05:57 PM   #15
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QuoteOriginally posted by K57XR Quote
I see what your saying with the samples, that is strange considering everything else is the same (iso, shutter speed) but exposure is nearly identical. I'm curious if those two samples are actually f4 and f29 respectively or the exif is inaccurate? Sorry, that doesn't really address your original issue, though. As for testing random aperture behavior as suggested by 6BQ5, I guess you can try mounting the camera on a tripod, 2-second timer and take a "camera-selfie" in front of a mirror? If that works the way I think it should you'd be able to see how big the actual iris is per shot. You may not be able to tell exactly what aperture it was but I can imagine the difference between f4 and f29 would be significant, then compare it to what the exif says - just a thought?

Also, your exif shows the camera is still running firmware 1.0, have you considered upgrading to the latest version (1.02)?
QuoteOriginally posted by 6BQ5 Quote
Just so you can see what the aperture blades are doing. That's all. Just snap away. The pictures you will take with your camera and store on the SD card are already paid for so start clicking.
Thanks folks. Sorry it's been so long. Here is a video of what the aperture blades are doing: https://www.flickr.com/photos/newarchivist/21359676453/in/album-72157658522799428/ I think this confirms it as well. The blades don't appear to be doing anything. In camera exif, at least, shows the f/3.5 for the first and f/22 for the second - with no change.

It's funny, the camera body still makes lovely photos when I'm using it with my 30 year old manual lens: https://www.flickr.com/photos/newarchivist/albums/72157659033235008

Do you all think updating the firmware would actually do anything here?

Again, thank you!
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