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K-70 Underexposed Photo Reports
Posted By: stevebrot, 10-05-2018, 02:16 PM

As of today, 28 December 2019, I will no longer be maintaining this report page.

The incidence is sufficiently low that it hardly makes sense, but it has been an interesting experience.

Steve

***************************************************************************************************

There have been a couple of recent threads regarding gross underexposure (essentially black) on some or all photos. While it is not fully clear whether these reports are related or (shudder) whether there is an emerging problem similar to the aperture block failure common to the K-30/K-50 models, it seems reasonable to provide a clearinghouse thread in an attempt to determine who is having problems and the evident point of failure. For the sake of clarity and accountability, it would be good to limit experiences to those of our users and not reference claims from other forums or rumor sites.

NOTICE: This thread is curated and keeping track of pertinent reports and updates will be easier if we abide be a few simple rules. Please use this thread for:
  • Reports of problems with underexposed or dark frames from Pentax Forums users. Please include written details and whether you were able to confirm that it is an issue with aperture control (see below for instructions).
  • Updates regarding cause, repairs, and repair details (when known)
Do NOT use this thread for:
  • Discussion of the aperture control block problem on K-30/K50/K500 models or reports for any model other than the K-70
  • Troubleshooting poor exposure. A separate thread in the K-70 subforum or in the troubleshooting section of the site might work better.
  • Photos of dark frames. If it is happening, your word is enough. Photo examples, even with full EXIF, are of limited or no value for troubleshooting or confirmation.
  • Complaints about Ricoh/Pentax product or service or business practices
  • Complaints or comments about the K-70 in general
  • Complaints about repairs from authorized facilities, including: timeliness, cost, outcome, or communication
In regards to the last three points, neither Ricoh/Pentax nor the authorized repair shops they contract with monitor activity on the Pentax Forums site.
**********************************

To date, I am aware of the following Pentax Forums users having problems with dark frames:

User @dudesohungry (31 Aug 2018) : K70 ISO problem - PentaxForums.com
Not known if this was an aperture or other problem.

User @drumhead (17 Sept 2018) : Strange behaviour from my K-70...aperture block? - PentaxForums.com
Presumptive aperture control issue. Camera sent for warranty service.

User @CodyH (30 Sept 2018): K-70 aperture motor question - PentaxForums.com
Confirmed aperture control issue with root cause not known. Warranty service may be attempted (camera barely out of warranty). Update -- camera is being sent for service and will probably be covered under warranty.

User @RichFam (5 Oct 2018): K-70 Underexposed Photo Reports - PentaxForums.com
Confirmed aperture control issue with root cause not known at about one year post purchase. Did not seek warranty service.

User @asalwa (11 Nov 2018): K70 aperture block? - PentaxForums.com
Confirmed aperture control issue with root cause not known, August 2018. Out-of-warranty repair was performed, though it is unknown what was replaced/adjusted.

User @Eric_Hall (10 Dec 2018): Dark images - PentaxForums.com
Confirmed aperture control issue with root cause not known with camera to be sent for service under warranty.

User @fernoh123 (6 Jan 2019): K-70 Underexposed Photo Reports - PentaxForums.com. Symptoms similar to aperture control issues with other model cameras. Unknown whether repair was sought.
Confirmed Camera was sent for warranty repair with root cause confirmed as aperture control block failure by statement of work performed.

User @pentax360 (30 Jan 2019): K-70 Underexposed Photo Reports - PentaxForums.com. Dark frames on first few captures of a session. It is unknown whether the cause is due to failed aperture control.

User @SharkyCA (31 Mar 2019): K70 aperture block? - Page 3 - PentaxForums.com.
Confirmed aperture control issue with root cause determined to be diaphragm control block. Dark frames interspersed with properly exposed frames (middle two out of four effected in initial report and many in subsequent discussion). User sent camera to Sun Camera in Canada where they confirmed the diagnosis.

User @disasterfilm (16 Jun 2019) New K-70 - Metering issues between Live View and OVF - PentaxForums.com originally reported as dark frames when using optical viewfinder only. This is apparently a metering issue, but is recorded here just in case.

User @Alex74 (10 Jul 2019) K-70 Exposure issues - Page 3 - PentaxForums.com
Ambiguous Aperture actuation problems of unclear nature (based on repair report); root cause ambiguous...repair report "exchanged aperture mechanism and controller". User initially reported severely underexposed as well as overexposed frames despite no change in camera settings. Initially it was unknown whether this was a problem of lazy aperture or aperture control. Making no assumptions, I trust that the problem has been fixed. Report is retained in the interest of making as complete a count as reasonable.

User @rwhynacht (15 Aug 2019) New K-70 - Metering issues between Live View and OVF - PentaxForums.com
Confirmed aperture control issue based on repair outcome; root cause ambiguous...repair involved replacement of Aperture Control Assy and Resistor Chip. NOTE: This camera had been recently purchased.
Severely underexposed photos in auto exposure modes that, though unclear whether the issue is metering or something else, but included here just in case. The camera was serviced with report noted here.

User @tanz (23 Aug 2019) K-70 Underexposed Photo Reports - Page 7 - PentaxForums.com reports severely underexposed frames when using the optical viewfinder with live mode not having obvious problems. Likely aperture control failure based on description of stop-down behavior.

User @riverrock (9 Sept 2019) https://www.pentaxforums.com/forums/193-pentax-k-70/377096-k-70-underexposed...ml#post4721041
Confirmed Aperture Control Failure/Issue, root cause unknown. Reports severely underexposed frames with visual confirmation of inappropriate aperture stop-down.

User @davedyer (12 Sept 2019) first picture is dark - PentaxForums.com
Confirmed aperture control failure/issue, root cause unknown. Reports underexposed first frame with properly exposed frames thereafter with visual confirmation of inappropriate aperture stop-down.

User @corbinco2 (25 Oct 2019) https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4778685
Confirmed aperture control failure/issue, root cause unknown. Consistent dark frames after two years ownership confirmed as aperture control problem by visual inspection.

User @Progbusters (19 Nov 2019) https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4818734
Confirmed aperture control failure/issue, root cause unknown. Consistent dark frames after a few months ownership confirmed as aperture control problem by visual inspection. Grey market purchase with unknown warranty options. User opted to not repair and sold camera "as-is".

User @photogem (23 Dec 2019) https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/377096-k-...ml#post4870093
Confirmed aperture control failure/issue corrected by user replacement of solenoid. Failure at after one year ownership, camera still under warranty.


**********************************


Three (initial) similar problems in less that a month's span are a potential cause for concern. Any future reports may be logged here in an effort to determine if these are isolated incidents or evidence of a larger issue. At the very least, this thread may serve to qualify claims of multiple reports from the Web regarding K-70 aperture control problems.

Note: Terminology is important and it is good to be clear on terms. Here are a few starters along with working definitions:
  • Exposure problems: images are over or underexposed. Cause may be anything from user inexperience to hardware meltdown
  • Metering issues: Bad meter readings leading to inappropriate settings
  • Dark Image Syndrome (DIS): Term coined by user @reh321 for unexplained dark frames despite correct settings
  • Aperture Control Failure/Issue: Iris opening during exposure does not reflect set value. Example: Camera is set to wide open, but exposure is made with lens stopped down to smallest opening. This sort of behavior may have many different causes as diverse as damage or failure in the lens itself and water incursion causing damage to body electronics.
  • Aperture Block Failure: This is the specific failure of the so-called aperture block solenoid used for aperture control on a wide span of Pentax SLR bodies dating back as far as the early 1980s. Failure of this component affected a large number of K-30, K-50, and K-500 bodies and was the cause of aperture control failure on those cameras. A similar unit was fitted to the K-S1 and K-S2. It is possible that the K-70 has a similar part, hence this thread.
  • Diaphragm control block : G100 Proper name and part number for the assembly that controls the aperture opening on most Pentax cameras since the early 1980s. "Aperture block" and "Aperture control block" are synonyms in common usage.
  • Diaphragm control block : G200 Proper name and part number for the assembly that controls the aperture opening on flagship models since the release of the K-7. As of 11 Oct 2018, it is not clear whether the K-70 uses this part or the G100 part above.

To test for Aperture Control Failure/Issue:
The so-called gold standard for diagnosing an issue with aperture control is to put the camera in M mode (auto ISO off, aperture ring not being used) with aperture set wide open and shutter speed at something slow (e.g. 1-2 seconds). Release the shutter while observing the aperture opening through the front of the lens. Anything other than the aperture remaining wide open is indication of a problem with the controller. If the problem has been intermittent, it may help to do the test after a period of non-use. Even one failure is significant.
Hopefully, there is no cause for alarm.


Steve

(...not a K-70 owner, but was heavily involved in the first wave of K-30 problems several years ago...)

Last edited by stevebrot; 12-28-2019 at 09:08 PM. Reason: Closing shop
Views: 18,620
12-29-2019, 12:45 PM - 1 Like   #151
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QuoteOriginally posted by SharkyCA Quote
Yes, thanks for the feedback! My post was to draw attention to the fact My camera was professionally repaired at a Pentax site and the part they replaced is pictured as they returned the used part to me which is identical to the part sold by USCamera.Pentax 77860-G0100 Diaphragm Control Block | K-S2 | K-30 | K-50 | PartsUSCamera Which appears to fit KS-2,K-30, and K-50.

Without an actual service manual displaying parts and part numbers a lot of information is speculative at this point!
Cheers!
Thank you for the photo.

The one thing that seems to be certain is that the problem seems less common on K-70 models than it was on K-30/50 ..... so there must be some kind of difference.

12-29-2019, 12:57 PM   #152
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Supposedly Ricoh has said changes were made although we don't what those changes are.
12-30-2019, 10:00 AM   #153
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QuoteOriginally posted by Not a Number Quote
Supposedly Ricoh has said changes were made although we don't what those changes are.
We do know that experience is showing a much lower "failure of aperture control" rate with the K-70, so they did 'fix' it somehow - but it still has cases of Dark Image Syndrome - for which the solution still seems to be replacing the solenoid - so the 'fix' is only a partial thing.
01-11-2020, 04:46 PM - 1 Like   #154
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Since Steve is no longer maintaining this thread, I'm closing it in order to preserve its original intent and prevent it from straying...

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