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04-18-2018, 01:01 PM   #1
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K-S1 first picture is dark

I haven't used the K-S1 much recently. Took it out today as it was the first hot day of spring, low to mid 20s and everything really starting to push on. Taking a few shots with firstly the 35mm f2.4, then a few more a bit later, and then a couple with the 100mm f2.8. In each of those three sequences, the first of each was underexposed by at least a couple of stops. I'll check again tomorrow, but I wondered if it was anything to be worried about or I just need to use the camera a bit more.

04-18-2018, 01:18 PM - 1 Like   #2
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Probably the actuator business, sadly. Pentax gear reacts to long rest periods with the aperture-block darkness on some bodies and SDM coma with those lenses. In the short run you can shoot in A mode at f/22 so the shutter speed is calculated correctly (and bump the ISO up a bit) - and read about both near-term and longer-term solutions to aperture block here on the forums.

I really like the 20Mpx sensor of the K-s series so I will probably take on this risk myself, some day soon.
04-18-2018, 01:20 PM   #3
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Check your settings, have you got exposure bracketing set where you will get one underexposed image, one correctly exposed and one overexposed?
04-18-2018, 05:08 PM   #4
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Could be bracketing inadvertently being activated. If not, then it could be the aperture issue. Feel free to post the shots and we'll be able to check the exif.


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04-19-2018, 06:54 AM   #5
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QuoteOriginally posted by Adam Quote
Could be bracketing inadvertently being activated. If not, then it could be the aperture issue. Feel free to post the shots and we'll be able to check the exif.
OK - here are two shots from yesterday, taken a minute apart. They've been through LR5 but no corrections applied, just exported to jpegs. I then used Preview to size them down for posting.

Is this going to be a repair job or a replacement job?
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PENTAX K-S1  Photo 
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04-19-2018, 09:35 AM   #6
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I just called the Pentax UK Tech Support line (which is re-routed to the Netherlands). So now I have a case number and await a reply from some tech. I'll post here how I get on.
04-19-2018, 12:32 PM   #7
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QuoteOriginally posted by Clothears Quote
I just called the Pentax UK Tech Support line (which is re-routed to the Netherlands). So now I have a case number and await a reply from some tech. I'll post here how I get on.
It does look like the aperture issue.


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04-25-2018, 02:24 AM   #8
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Update: the tech asked a number of questions including whether it happens in live view. I couldn't answer that one as I never use live view, which, when I tried it, seemed to shove a load of junk on the screen which it took me a while to get rid of. Anyway, it seems that it's OK in live view.

After some tests it seems that it's reproducible that in non-live view, the problem is present whenever the camera has been off for a couple of hours. There is some evidence that, if I turn the camera on, then turn on live view, then turn live view off, that the first shot I then take is OK (and subsequent ones, obvs).

I'll continue testing like this, sometimes doing the LV shuffle, sometimes not, to see if LV on/off constitutes a workaround.

I have it in mind also to do the following: I suppose that it could be the aperture arm not moving as directed by the camera (not a lens problem as this happens with several lenses), or it could be the shutter. So, I'm thinking of taking shots of myself in a mirror, to see whether or not the lens iris is opening to the requested aperture.
04-25-2018, 04:12 PM   #9
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QuoteOriginally posted by Clothears Quote
I haven't used the K-S1 much recently. Took it out today as it was the first hot day of spring, low to mid 20s and everything really starting to push on. Taking a few shots with firstly the 35mm f2.4, then a few more a bit later, and then a couple with the 100mm f2.8. In each of those three sequences, the first of each was underexposed by at least a couple of stops. I'll check again tomorrow, but I wondered if it was anything to be worried about or I just need to use the camera a bit more.
Wander over to the K-30&50 section and you'll find many long and sometimes contentious threads about the aperture issue, but here is one to get you started
Dark exposure problems on K-30 or K-50? Read me first! - PentaxForums.com
05-01-2018, 01:37 AM   #10
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QuoteOriginally posted by Clothears Quote
I have it in mind also to do the following: I suppose that it could be the aperture arm not moving as directed by the camera (not a lens problem as this happens with several lenses), or it could be the shutter. So, I'm thinking of taking shots of myself in a mirror, to see whether or not the lens iris is opening to the requested aperture.
I tried this with Av mode, using a couple of lenses set to just below maximum aperture. With an OK shot, I could see the iris open OK. Unfortunately all the dark shots were so dark that nothing could be recovered from the image. So that test failed.

The Pentax tech was asking about live view so I've reported back on that and am waiting to hear more.
05-14-2018, 02:22 PM   #11
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QuoteOriginally posted by Clothears Quote
I tried this with Av mode, using a couple of lenses set to just below maximum aperture. With an OK shot, I could see the iris open OK. Unfortunately all the dark shots were so dark that nothing could be recovered from the image. So that test failed.

The Pentax tech was asking about live view so I've reported back on that and am waiting to hear more.
Well glory be. They've finally asked for some images, so I sent them a sequence of three, each about 15 secs after the previous (single shot, Av, f2.8, 100ASA, 1/125 sec). These range from essentially black to OK.
06-05-2018, 02:16 PM   #12
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Update

Tried the camera today: had to take 8 shots before I got a properly exposed one, so it could be getting worse.

After I sent the duff images to Pentax, their response was that I should send it to the official UK repair place to get it seen to. Then we were away for a week, so just packaging it up now to be sent off tomorrow. Had to do some hunting around but finally found the original box and the body mount cover.

Fingers crossed.
06-11-2018, 09:25 AM   #13
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News from the repairers: cost to repair estimated at £113 (including VAT and return shipping) so I've accepted that.

They expect to:

REPLACE MECHANICAL ASSY
REPAIR SHUTTER MECHANISM AND MIRROR MECHANISM
CHECK AND CLEAN VIEWFINDER ASSY AND CCD

which seems fairly comprehensive but I wonder what provoked it.
06-11-2018, 12:08 PM   #14
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QuoteOriginally posted by Clothears Quote
News from the repairers: cost to repair estimated at £113 (including VAT and return shipping) so I've accepted that.

They expect to:

REPLACE MECHANICAL ASSY
REPAIR SHUTTER MECHANISM AND MIRROR MECHANISM
CHECK AND CLEAN VIEWFINDER ASSY AND CCD

which seems fairly comprehensive but I wonder what provoked it.
Most likely, the aperture failed and you did the natural thing, taking a burst of pictures for each image you wanted. Unfortunately, for a camera like this, the shutter / mirror can handle only so much of that.
06-11-2018, 12:52 PM   #15
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QuoteOriginally posted by reh321 Quote
Most likely, the aperture failed and you did the natural thing, taking a burst of pictures for each image you wanted. Unfortunately, for a camera like this, the shutter / mirror can handle only so much of that.
Nice hypothesis, but contradicted by the facts. During the time this problem has existed, I have never taken pictures in burst mode, always single shot. Actually, I reviewed each shot before taking the next one, to see if the camera was back to normal.

(In fact, I have never used burst mode in the time I've owned the camera.)
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