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09-20-2021, 03:30 PM   #16
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QuoteOriginally posted by RobSpain Quote
Right, I've just tried the DoF simulation using LV and the first shot is OVER exposed as per my original post above. Thereafter, every shot is exposed correctly. So if nothing else, the fault is very consistent! Does this mean that I have a solenoid problem, or not?
Aperture control issues related to the solenoid have UNDER exposure as their presenting symptom.

May I ask, does this happen regardless of lens mounted?


Steve


Last edited by stevebrot; 09-20-2021 at 03:35 PM.
09-20-2021, 03:46 PM   #17
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OK...lets cut to the chase...

Can you provide two (on UNDER and one OVER) straight-out-of-camera file with EXIF intact that we can take a look at?


Steve
09-20-2021, 09:09 PM   #18
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QuoteOriginally posted by stevebrot Quote
OK...lets cut to the chase...

Can you provide two (on UNDER and one OVER) straight-out-of-camera file with EXIF intact that we can take a look at?


Steve
Sounds exactly like Aperture block failure. I had exactly the same issues until my failed completely. Pentax returned a dead green solenoid on the bag of parts replaced.
Greg
09-20-2021, 10:12 PM   #19
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QuoteOriginally posted by Greg1956 Quote
Sounds exactly like Aperture block failure. I had exactly the same issues until my failed completely. Pentax returned a dead green solenoid on the bag of parts replaced.
Greg
I guess that explains the second shot always being over-exposed? The pattern is the puzzle here.

BTW...OP said they did the aperture function test and the camera passed.


Steve

09-20-2021, 10:49 PM - 1 Like   #20
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My symptoms were over exposed, under exposed then ok.
Repeated over a couple of months.
Would start the day by shooting multiple exposures until it came good, then one day all black.

Replaced the solenoid.

I wasn't aware that there was a test for aperture block failure, sounds interesting.
Greg
09-21-2021, 01:45 AM   #21
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Last night I updated the K-70 firmware from V1.12 to V1.13. No difference, insofar as the problem still persists.


But as I have explained before, the problem only appears after the camera has been switched off for at least a couple of hours. The first shot is then underexposed using the OVF and overexposed using LV. Thereafter I can run as many shots as I like at high or low speed shutter speeds, large or small apertures, high or low ISO, burst shots, and ALL are perfectly exposed. If I switch the camera on and off quickly various times, the problem DOES NOT arise and the first shot and subsequent exposures are all correct. It appears that when the camera has been off for a while, it struggles only on that first shot. Juice problem?


With regard to exif data, the underexposed first shot (using OVF) shows identical data to that of the correctly exposed (second) shot. However, when using LV, the exif data shows different settings for the overexposed shot, a one-stop slower shutter speed.


I haven’t tried the reset as yet as I have the camera very finely tuned to my liking and don’t wish to have to set it all up again. But if the problem gets worse then I’ll try this.


My feeling is that it could potentially be the beginning of an aperture failure but I’ll have to see how it develops. For the moment I can live with a FIRST SHOT failure. As long as the camera continues to perform like this, then fine. If it gets worse, then it’ll be a repair job.

---------- Post added 09-21-21 at 11:34 AM ----------

Oh dear! I've just switched the camera on again after less than an hour, and I've got my first BLACK shot. Completely underexposed. Subsequent shots are fine but I think the writing's on the wall!
09-21-2021, 06:07 AM   #22
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Just during the course of today the shutter is now acting very erratically. I'm now getting loads of overexposed shots with LV. The camera does settle down after a few shots but there's no doubt that it has a serious problem. So ANOTHER K-70 bites the dust!


BTW I've just checked the manufacture date and shutter count by uploading a jpeg from the camera to the relevant page here on the forum:

Manufacture date: 31/05/2017
Shutter count: 18,482


So a much lower shutter count than I imagined!

09-22-2021, 12:57 AM   #23
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QuoteOriginally posted by stevebrot Quote
Aperture control issues related to the solenoid have UNDER exposure as their presenting symptom.

May I ask, does this happen regardless of lens mounted?


Steve
I've tried it on two different lenses, the 18-50mm kit and the Sigma 10-20mm f/3.5 and the results are the same.

---------- Post added 09-22-21 at 09:58 AM ----------

QuoteOriginally posted by Greg1956 Quote
Sounds exactly like Aperture block failure. I had exactly the same issues until my failed completely. Pentax returned a dead green solenoid on the bag of parts replaced.
Greg
Do you know if they replaced it with the same green one?
09-22-2021, 03:27 AM - 1 Like   #24
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QuoteOriginally posted by RobSpain Quote
Just started to have an unusual experience with my K-70. When switching on (after the camera has been OFF for a few hours), the very first shot using the OVF is UNDER exposed. Again, with the camera OFF for a while and using LV, the very first shot is OVER exposed. Thereafter, using either OVF or LV all shots are perfectly exposed. I was using a fully charged battery. To ensure it’s not a lens problem, I’ve repeated the above using both the 18-50mm kit lens and the Sigma 10-20mm f/3.5, with the same result. I’ve also tried this test on a daily bases for the last couple of weeks and the reoccurrence is as regular as clockwork!

The camera is 3 years old with around 30,000 shots, mostly HDR as I use the camera for real estate photography. I’ve not had any problems up to now but this started just recently. Of course I’ve read much on the subject of K-70/K-50 etc. shutter failures but I don’t think I’ve ever seen a post detailing the above abnormality of 1 under and 1 over, and thereafter everything OK.

Any thoughts?

TIA! Robert
I had problems with the internet for a few days, so late reply:
First do those tests:
How to detect aperture-block failure/stuck solenoid on Pentax K-70 - PentaxForums.com
It is simple because its done in Av-MODE which is familiar to you.

The overexposure in LV-Mode is possible because it can happen that the solenoid does stay open for a short time.

But the guidelines in the tutorial are very clear and should give clear results.
09-22-2021, 05:11 AM   #25
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QuoteOriginally posted by photogem Quote
I had problems with the internet for a few days, so late reply:
First do those tests:
How to detect aperture-block failure/stuck solenoid on Pentax K-70 - PentaxForums.com
It is simple because its done in Av-MODE which is familiar to you.

The overexposure in LV-Mode is possible because it can happen that the solenoid does stay open for a short time.

But the guidelines in the tutorial are very clear and should give clear results.
Thanks for this but I've already tried that page. I'm only getting the problem when the camera has been off for at least an hour, or overnight. Having said that, this morning i switched on the camera and started to go through all camera settings to see if something was amiss. Upon checking the 4-way controller i found that the flash setting was on Full Manual Flash Discharge. Given I never use the on-board flash (I always use external units), I reset it to its normal ON mode. At this point I hadn't taken a shot or actuated the LV. I then took a shot and the first exposure was fully correct, something I didn't understand given the described fault was ONLY happening when switching on after a prolonged period.


So then I thought I'd try using a flash to see how the camera performed and see if I was getting incorrect exposures. I used an external flash in TTL mode in both auto and manual and all shots came out fine.


I've been playing around all morning and whilst the camera stays on, or if I switch off for a short period then on again, I'm not having the problem. I've even tried 5 exposure HDR and the results are correct! The under and over exposure fault only happens when the camera has been off for a while. But, as I've mentioned earlier in this post, I have had one BLACK completely underexposed shot, so I know something's not right.


It's very frustrating.


I've been in touch with the official repair centres here in Spain. The official Pentax importer wasn't very sympathetic. The other thinks it might be the pre-diaphragm unit and said it wasn't a problem to replace but I haven't got a price yet. Then I found Alan Marlow in the UK and he said he can fix the issue no problem. I have since done a Google on him and everyone rates him extremely highly, I couldn't find a bad comment anywhere. So I may use him. He's quoted just 95 GBP with a 6 month guarantee!


So I will keep this post informed...
09-22-2021, 10:06 AM   #26
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What would be the most useful:
Upload a few incorrect exposed photos.
No flash, only AV and starting with wide open. This is photo #1
Best with a prime such as the DA50/1,8.
Start with 1.8, then 2,0, then 2,4 etc. up to f22

Also when you turn the camera round, look, into the lens and then switch LV ON: Does the diaphragm to into f4,0 or is completly closed

As I said, instructions are very clear.
To get "not frustrating answers" you need to follow these steps exactly and give exact answers/samples.

Don't misunderstand, but defining if the solenoid is gone is more or less an exact science.
09-22-2021, 12:52 PM   #27
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QuoteOriginally posted by RobSpain Quote
Just during the course of today the shutter is now acting very erratically. I'm now getting loads of overexposed shots with LV. The camera does settle down after a few shots but there's no doubt that it has a serious problem. So ANOTHER K-70 bites the dust!
Perhaps.

It struck me yesterday evening that I broke one of my own rules for dealing with troubleshooting poor/unexpected exposure issues. That being that the first thing to determine is whether the exposure matches the camera settings. For example, say the meter indicates 1/125s and f/5.6 (fixed ISO) in M mode when the subject is a patch of grass and nothing else. Do those settings result in an image of that grass having reasonable brightness?

In your case, the question is whether the result is consistently the same brightness for the same 1/125s, f/5.6 setting. If not, there is mechanical problem.


Steve
09-23-2021, 01:24 AM   #28
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QuoteOriginally posted by stevebrot Quote
Perhaps.

It struck me yesterday evening that I broke one of my own rules for dealing with troubleshooting poor/unexpected exposure issues. That being that the first thing to determine is whether the exposure matches the camera settings. For example, say the meter indicates 1/125s and f/5.6 (fixed ISO) in M mode when the subject is a patch of grass and nothing else. Do those settings result in an image of that grass having reasonable brightness?

In your case, the question is whether the result is consistently the same brightness for the same 1/125s, f/5.6 setting. If not, there is mechanical problem.


Steve
The basic answer to your comment is yes, they are consistent, ONCE I've got over the first UNDER exposed shot using OVF (or OVER exposed in LV) when switching the camera on (after at least an hour in off).

Furthermore, yesterday i ran a whole series of 5-exposure HDR shots at +/- 2.0 EV, and compared the middle exposed shot (0 EV) to a manual shot of the same scene, and the both the exposure and exif data were identical. I did this test several times.


Here's another observation: As I use my camera regularly I never take the battery out, but always start a shoot with a fully charged one. However, for last 2 days I have removed it overnight. Both yesterday and this morning upon inserting the battery, switching on, and taking the first shot in the OVF, the first shot was NOT under exposed. I am not a technician or electrical engineer so I don't know what to conclude from this. I just mention it anyway in case someone can interpret this.

I'm gonna go and shoot some photography this weekend, give the camera some stick and see what the results are like. Whilst the camera performs, I'll hang on before sending it for repair.

---------- Post added 09-23-21 at 10:37 AM ----------

QuoteOriginally posted by photogem Quote
What would be the most useful:
Upload a few incorrect exposed photos.
No flash, only AV and starting with wide open. This is photo #1
Best with a prime such as the DA50/1,8.
Start with 1.8, then 2,0, then 2,4 etc. up to f22

Also when you turn the camera round, look, into the lens and then switch LV ON: Does the diaphragm to into f4,0 or is completly closed

As I said, instructions are very clear.
To get "not frustrating answers" you need to follow these steps exactly and give exact answers/samples.

Don't misunderstand, but defining if the solenoid is gone is more or less an exact science.
Unfortunately, I don't have any more 'credit' left here on the forum to upload any pictures. Please see my reply to stevebrot above to see that I have tested out the camera extensively by comparing a series of HDR and manual shots. I have also performed tests such as you have suggested at different speeds, apertures and ISO and then compared the results. The results are consistent and evenly exposed.


Regarding: "Also when you turn the camera round, look, into the lens and then switch LV ON: Does the diaphragm to into f4,0 or is completly closed"... I switched on, set the aperture to f3.5 on a Sigma 10-20 lens, switched to LV, looked into the lens and yes the aperture closed to that setting. Bear in mind though that the camera had only been switched off about 20 minutes.


As I have emphasised various times in this post, the problem arises only after switching the camera on after a period in off of at least an hour. Hence my comment about removing the battery (in previous comment above) and whether this has any bearing, or not.

Last edited by RobSpain; 09-23-2021 at 01:41 AM.
09-23-2021, 02:02 AM   #29
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If the same results are achieved with the K70 not being used for a longer period, i.e. the diaphragma is open to f3.5
then it is not (yet) the solenoid. Only if the result would be a almost black picture wide open and at the same time you can notice the diaphragma is closed to f22, then you know the solenoid is part of the problem.

Usually if the 1-st shot is underexposed this is a sign that the solenoid is going to become a problem.
After a while it will be more "dark shots".
09-23-2021, 02:18 AM   #30
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QuoteOriginally posted by photogem Quote
If the same results are achieved with the K70 not being used for a longer period, i.e. the diaphragma is open to f3.5
then it is not (yet) the solenoid. Only if the result would be a almost black picture wide open and at the same time you can notice the diaphragma is closed to f22, then you know the solenoid is part of the problem.

Usually if the 1-st shot is underexposed this is a sign that the solenoid is going to become a problem.
After a while it will be more "dark shots".
This is my belief too. I have had just ONE black shot 2 or 3 days ago. So I think it will get worse with time. If so, then off to the repairers!
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