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A LITTLE BIT OF HISTORY: Development of the solenoid in Pentax cameras
Posted By: photogem, 06-27-2019, 01:50 AM

A little bit of history about the development of the solenoid in Pentax cameras up to the K-70:

The legendary patent named "Automatic Camera Shutter" was applied for July 30, 1968 and granted Jan. 4th, 1972.

You can down load the patent HERE


1. The first very simple solenoid I have found in the Pentax ME and ME-Super.

No permanent magnet yet but only a plunger and an electro-magnet to induce the magnetic force to pull the plunger:



It was in 1983 that Pentax introduced its first SLR which offered fully automatic exposure ("program") mode when coupled with a matching Pentax-A series lens:
The Pentax Super-A (Super Program), followed by the Program Plus (Program-A) in 1984.



This was the first time solenoids where used the way we know it until today up to the Pentax K-70.

2. A very nicely built and sophisticated solenoid:





Not yet a rare-earth-magnet as later used but an alnico-magnet, i.e. an alloy mainly of al-uminium, ni-ckel, co-balt, invented by T.Mishima 1931 in Japan:


Backside:


The solenoid in action:





The force of this alnico magnet pulled a kind of cap connected to the leaver which moved the aperture-mechanism and kept it in place.
Taking a picture, the two coils acting as an electro-magnet receive 3 Volts DC from the cameras battery ( 2 x 1,5V SR44 or 1 x 3-V CR1108).
Those 2 coils cancelled the magnetic force of the permanent magnet and the top-cap opened, the leaver moved. Impedance was 14,3 ohms.


The electro-magnetic coils:


The partnumber given was G-100:


This partnumber G-100 remained the same at least up to the Pentax K20D and K200D, possibly later on as well but I have not yet seen a service manual of those.
Samsung named it G-100 as well in the GX1, GX2, GX10 and GX20.


The next solenoid as we know it was introduced in some the MZ-Series (MZ50, MZ6, MZ7 and a few others up to the 35mm Pentax *ist).
This Solenoid was manufactured by Shinmei Electric Co., Tomioko-Cho, Futaba-gun, Fukushima, Japan (see 3.a) and by TDK, Japan (see 3.b)
Those solenoids were also sold to ALPS and Matsushita.


This first SLR Shinmei and TDK solenoids look identical to the later DSLR made in Japan versions and had the same impedance.
This solenoid was driven with 6V/DC (rated with 4,5V/DC) by the solenoid-driver, impuls-voltage was 6.45V.
Thus the holding-force and body thickness were slightly different and sometimes with opposite polarity. It is not recommended to use it.


3. a) Here a photo showing the 3.rd version of a solenoid, this one I took from a MZ50 tested in a K30:

One can see, the plunger tilts slightly in relation to the round part of the leaver which it moves.

The next drawing shows this early SLR solenoid (i.e. not yet DSLR!):


It has 3.4mm bobbin-size (versus 4mm bobbin-size for the later DSLR-solenoids).

Data Japan-made "SLR" solenoid:
- Operating Voltage DC: 3 - 6V
- Coilresistance: 30 ohms
- Attraction force: 2,2 N min
- Backtension: 0,8 N
- Operating stroke: 2mm


3.b) To make things more complicated, Pentax also used a white Japan made SLR solenoid made by TDK:


The early introduced MA-307-9 was developed for 3-6V use (2 x CR2 /900mA) = so for the 35mm SLR Pentax of the MZ/XZ-Series!

And most important: The bobbin thickness was 4m and not 3,2mm as the Shinmei-version. So even more difficult to differentiate from the DLSR version!

Later they introduced the MA-307-26 für 3,7-6,5V (2 x CRV3/3300mA!) = DSLR *istDS/DL, K10D

What can be seen very cleary is the difference in holding-force (attracting force) and return-force (back-tension)


4. A very different solenoid was used in many other MZ/ZX such as the MZ5 bodies:





4. With the introduction of the Pentax *ist D came the "made in Japan" white DSLR solenoid which never failed in any of those bodies up to the Pentax K-r:


The manufacturer of those solenoids remained Shinmei, Japan and manufacture was in Japan.


The next drawing shows that this new introduced Shinmei Japan solenoid for DSLR bodies had now a 4mm bobbin-size instead of 3.4mm:



As mentioned, this difference of 0.6mm is hardly noticable but this is why aside from another small difference in holding-force and often opposite polarisation the early SLR solenoids with 3.4mm bobbin-size sit slightly bent when installed into a DSLR body!
This DSLR Solenoid had a live-timespan of remarkable 100.000 actuations but lasts actually much longer.


Data Japan-made "DSLR" Solenoid:
- Operating Voltage DC: 3,6 - 7,2 V- Coilresistance: 30 ohms
- Attraction force: 2,5 N min
- Backtension: 1,0 N
- Operating stroke: 2mm

According to an engineer who worked for Pentax and with teams designing cameras (I have the email from him as prove)as well according to a Ricoh representative from France the material used was a mix of PTFE's (Teflon) and thus it could be injection molded. I cannot guarantee this to be the case but there is no reason not to believe specialists.



5. Green-China-Solenoid

When Shinmei moved production to China, difficulties started!
Shinmei was now the sole provider to Ricoh for Pentax DSLR cameras!

Manufacturing place was now in Shanghai. Problems due to saving costs arised, such as bad pay and bad treatment of workers

Manufacture in Tomioka, Japan, stopped earlier on but the plant itself was finally shut-down in 2010.
This means not more manufacturing possible in Japan.


The material of the body changed to the green colour and instead of using a mix of different PTFE's (teflon) it was now made out of PET.

The alloy of the plunger changed as well.

PTFE (teflon) is a very good bearing material, it is used as well for bearings in turntables. This bearing was patented by W. Firebough. He describes the bearing very well in This interview. I could verify the amazing bearing qualities myself. When one inspects a heavy used Japan-solenoid closer against one made in China, one can tell the difference, PET is worn off much quicker.

This China made solenoid was first used in the flash circuit of the Pentax K100D (year 2006), K100D, K200D, K-m, K-x and K-r (until year 2011) but as far as I know mainly in those delivered to Europe. So a testing period of 5 years without any failure.

Rated voltage was now 3,7 - 7.5V (impuls 8.32V) but live-time was drastically lower: 20.000 actuations.

Data China-made solenoid
- Operating Voltage DC: 3,7 - 7,5V
- Coilresistance: 30 ohms
- Attraction force: 2,8 - 3,0 N min
- Backtension: 1,2 N
- Operating stroke: 2mm


Here you can see the measurements on a Pentax K-30


The next drawing shows the datasheet of the green China-solenoid:

The dashed (----) line shows the 30ohms version used for Pentax. The lower live-time of 20.000 actuations is due to PET instead of PTFE used in the early Japansolenoid.

Some claim (without prove, because it cannot be proven) that the voltage used for the Chinasolenoid would be more in the region of 2.5V because it releases smoothly at 2.5V. That's a lot of nonsense because none, the early Japan made SLR, the next Japan made DSLR solenoid nor the China made version work well with just 2,5V/DC! They kind of work with 3V but are driven with 6V in the SLR Pentax cameras and 7.2V in the DSLR Pentax cameras.
If one studies the curve for holding-force one can see this very clearly! I have done tests with 3V, 6V and 7.2 Volts. Measuring release-time (and thus holding-force) can be done from 5V - 9V. If one compares different solenoids it just is important that the applied voltage is the same for all solenoids one compares! The applied Vpp since the Pentax *ist-D is exactly 8.32VDC. Earlier pre DSLR bodies such as the MZ50 had 6VppDC.

The solenoid is driven by a transistor (BJT/SOT23) and protected by a simple diode.


While the China-made solenoid was tested in the flash-circuit, the solenoid used for aperture-control remained still the white made in Japan unit!
This test-period went on for about 6 years (the K100D was introduced 2006, the K-30 introduced 6 years later in 2012).
So 6 years without trouble, enough time to use it for the aperture control.

This photo shows the green China solenoid for the pop-up-flash in a K200D:



And here built out:




This change to manufacture in China turned out to be the beginning of difficulties due to several reasons described here as well
and led to a problem now known as:

ABF = Aperture Block Failure (also named: "dark-image-syndrome" or "dark exposure problems")

The plunger of this solenoid suddenly didn't release anymore but remained stuck! The diaphragm/blades/aperture of the lens could not open and
thus particular wide open and low f-stops (f1.4 / 1.7 / up to f 8) resulted in totally underexposed pictures, almost dark/black. If one changed to fully closed (such as f22) one gets a normal exposed picture.

For quite a long time it was not yet clear that the cultprit was just the solenoid!

The complete "diaphragm-control-block" was exchanged or possibly just the whole camera because exchange of the block was very work + time intensive. But then due to all the research mainly here in this forum (!) Ricoh/Pentax realized that it was just the solenoid itself.

It was about Dec. 2015 that Ricoh started to modify the solenoid which we now call the

6. "2.nd generation China-Solenoid":

But quite a lot KS-1's, K-S2's and many K-50's and all K-500's still used the earlier 1.st generation China-made green solenoid because they were manufactured prior Dec.2015! Thus quite a lot of them failed and do still fail.

This is mainly due to fact that the metal body + plunger of the China-Solenoid is made out of relatively higher coercivity material:
It thus retains its magnetism after the field strength is removed!


This also explains why in many cases ABF happens more to those Pentax bodies which hadn't been used for a longer period and/or those with a low shuttercount (a low shuttercount implies little use anyway up to the case of two NOS Pentax bodies which I repaired, they hadn't been used at all but cought ABF, so the best proof for this explanation which I got from a forum-member who is a Chartered Electrical Engineer with Nuclear Electric.

It is very simple: When the Pentax is not used the plunger sits all the time near the permanent magnet and the magnetized body.
No use will enhance the "glueing effect", i.e. the solenoid sticking inside the body.
Regular use is no guarantee but it is clear and researched that ABF happens less often.

!!! The holding force of this 2.nd generation China-Solenoid was still stronger compared to the Japan-made Solenoid !!!
and it does not fire as quick.


Close-up photos of the solenoid used in the K-70 show now a very nicely machined plunger with a smoother surface:



Very different to the surface of a solenoid modified by filing or sanding:

The surface of the alloy which is hurt by sanding or filing starts to corrode and can actually rust pretty bad.


So due to the still stronger holding-force and the alloy
it turned out that this 2.nd generation China-made solenoid wasn't perfect yet!


ABF happened less but there were still reports of K-70's failing.

Some repairshops tried to deflect from the true cause (the solenoid) and invented a socalled "resistor-chip" which now would fail and cause the solenoid to stop working correctly. We had some hot heated discussions about it, it turned out to be a fairytale and the repairshops quickly stopped "exchanging resistorchips".


6. Fake Solenoids (but recommended by their sellers to be suitable for Pentax = Fake facts)

a) Meanwhile more and more green solenoids turned up on ebay, ali-express etc.
If purchased in quantities via alibaba China one single solenoid was just a few cents, BUT:
Those are even inferior and were NOT MADE FOR DSLR but for Lenovo DVD-drives:


You can see, the 2 pins facing sideways are missing!

The permanent magnet is longer and stronger and thus they have a way too strong holding force!

They were constructed for a very simple "press-button-open-tray" circuit


Beware of those by all means!


b) Beware of Blue-coloured China-Solenoids from ROM-Drives:

Wrong impedance (15ohms)! Danger of exodus for the "solenoid-driver".


c) And of course:Beware of green solenoids which are filed/sanded!

Further information why you should avoid this you can study HERE

d) Some sellers on ebay offer white Japan solenoids which actually are SLR solenoids, no matter if 4mm bobbin-size made by TDK!
See 3.b)


Further Warnings: (based on long-time and verified studies)

- Lubing: Beware of any attempt to lube the plunger of the solenoid!
Even very thougthful attemps or rubbing graphite-powder into the plunger didn't solve it.
WORST Scenario I ever came across was to spray contact-cleaner or similar stuff from HERE, i.e. the mirror-box towards the region of the solenoid. You don't want to spray anything inside your camera, most sprays contain oily ingredients such as naphta or petroleum together with fast evaporating ingredients to make it dry quickly. The worst that can happen is if such stuff comes into contact with the mirror or hinged submirror, damping material for the mirror, the shuttercurtain of your sensor.
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


With the Pentax K7 Pentax introduced a stepper-motor instead of a solenoid. This demands a different powersupply, more current from the battery, extra space within the body, i.e. the body has to be larger plus some weight. This stepper-motor was used in the K7, K5, K3, KP and K1.

Size comparison of the stepper motor on its board against the solenoid:



7. GOOD NEWS:
3.rd generation green China-solenoid used since Jan. 2021 in the K-70
and of course now the KF:



Shinmei changed the size of the magnet, it is again shorter and thus has less magnetic power.

Here you can see all 3 stages of the China-solenoid (plus the very bad Lenovo solenoid on the right side):



So we have 3 steps of the China-made green solenoid used since the K-30 in the aperture block:


- Verson 1: The non-modified version as we know it was used until Dec. 2012, less clear defined dimple in the plunger

- Version 2: The 1.st modification as used since Dec. 2012 with a smaller magnet, changed alloy and clear defined dimple in the plunger

- Version 3: The 2.nd modification: Same alloy as in the 1.st modification but even shorter magnet (since Jan. 2021)








Last edited by photogem; 09-28-2023 at 06:17 AM. Reason: Latest info added by Photogem
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05-25-2020, 05:03 AM   #16
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Cool stuff. Great pictures.

05-25-2020, 09:08 AM   #17
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QuoteOriginally posted by normhead Quote
Cool stuff. Great pictures.
My ks2 was manufactured in May of 2017, and it failed as well.
05-30-2020, 03:10 AM - 1 Like   #18
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That is a true horor story. it shows a firm with very little quality control and a bad morale. A decent firm had taken hands on the problem, stopped using and given free exchange of the green soleonid.
I have a K30 with problems and a KP. My first KP was replaced after a few months.. The actual KP is good - hope it lasts - if you can overlook the imprecise pdaf.
Following several threads I now know that I am asking for too much of the pdaf.
BUT my impression is that the rate of succes was better on the K 30.
Together with a freind we have tested the rate of succes on his Nikon 800. It was not impressing either.
I dont know if the Pentax morale is worse than other firms- I doubt. The factories make cameras for the shareholders, not the photographers.
I love and use the m 42 Pentaxes
05-30-2020, 03:46 AM - 1 Like   #19
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QuoteOriginally posted by niels hansen Quote
The factories make cameras for the shareholders, not the photographers.
And the May 2020 award for barmy business commentary goes to the above quote.

05-30-2020, 06:58 PM   #20
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QuoteOriginally posted by niels hansen Quote
That is a true horor story. it shows a firm with very little quality control and a bad morale. A decent firm had taken hands on the problem, stopped using and given free exchange of the green soleonid.
I have a K30 with problems and a KP. My first KP was replaced after a few months.. The actual KP is good - hope it lasts - if you can overlook the imprecise pdaf.
Following several threads I now know that I am asking for too much of the pdaf.
BUT my impression is that the rate of succes was better on the K 30.
Together with a freind we have tested the rate of succes on his Nikon 800. It was not impressing either.
I dont know if the Pentax morale is worse than other firms- I doubt. The factories make cameras for the shareholders, not the photographers.
I love and use the m 42 Pentaxes
This is a very bald comment.

What do you mean by "success"?
What were symptoms of the first KP?
Was the first KP replaced under warranty??
What does your experience with a KP have to do with these words about the solenoid???
05-31-2020, 03:09 AM - 2 Likes   #21
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QuoteOriginally posted by niels hansen Quote
That is a true horor story. it shows a firm with very little quality control and a bad morale.
Not so easy, but it is very easy to judge:
As I wrote in my first post, the green China solenoid was tested for several years in the K100D, K110D, K200D, Km, Kx and Kr.
But only in the flash circuit, maybe because exchanging it if it would fail would be easier and faster than the one used for aperture control.
It never failed there!

So they felt it would be save to use it for aperture control as well because stock of the Japan-Solenoid was running short.

It was only after about 1 year when the first faults turned up, often under warranty, so one hardly heard of the problem.
Then it was said that the complete diaphragm-control-board was replaced, I heard different, i.e. they just replaced the camera, because exchanging the diaphragm-control-unit takes many hours to do so, it is more work than to replace the sensor! When we had the K5 sensor stains, as far as I know Pentax replaced the complete camera on warranty!


I have disassembled a K30 once to replace this unit, the steps can be studied here at the end of my first post
That's why I am also very weary when people tell me they disassembled their Pentax completly to get to this unit.

Anyway, the rest is explained in my first post in this thread and in many countries Ricoh did offer good solutions outside warranty times. Not always but hell.... there are similar stories of 1001+ other companies.
05-31-2020, 05:50 AM - 1 Like   #22
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My point is that companies primare goal is profit, costumer care is executied if it is profitable in the long run. The companies are not interested in the costumers, they are interested in our money.

reh321

I Mean the rate of af presicion.

My first KP was the first in Denmark, it came from Sweden I bought it because the K30 became unrealibel, did not know of the solenoid problems.
The problems were AF and batterilife. The camera was sent to Holland and was replaced under warrenty.
My experience with tke KP is not directly correlated to the soleonid scandale. It is reflections about the quality of Pentax - and probably others.
Cameras today are very sophisticated, maybe they are not sufficiently tested before launched
For the moment I am satsified witth the KP, exept the performence when taking spontaneous portraits of kids, where reliabel AF is essentiel. Being 77 years old MF is not realistic with the KP
BUT my experience with two defective Pentax Dslrs make me nervous. Will other problems occur - and when?
Talking with my freinds indicate that other brands are not better.
The Spotmatc from 68 is my lifebelt Two years ago it got a CLA.

photogem
Your article is splendid, but you write that Pentax felt that the green solenoid was good enough to use in another way.
Feelings are not testing. carefull testing under relevant conditions is a must. You dont test Wellingtons in Sahara

Perhaps my bgigest mistake was going digital. For the investment I could have bought tons of film and so on.
I hope that my english is good enough in this case

06-01-2020, 03:03 AM   #23
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QuoteOriginally posted by niels hansen Quote
photogem
Your article is splendid, but you write that Pentax felt that the green solenoid was good enough to use in another way.
Feelings are not testing. carefull testing under relevant conditions is a must. You dont test Wellingtons in Sahara

Perhaps my bgigest mistake was going digital. For the investment I could have bought tons of film and so on.
I hope that my english is good enough in this case
Your English can be understood well enough, don't worry about it.
Funny enough you wrote something which you mean differently, but luckily one cannot test/measure "feelings"!
It would be terrible if one could. One can only feel them if one has them.


Anyway: If you would be able to understand Japan, business over there, rules etc. and.... the importance of beer behind the scene (I am not kidding)
then you could see that actually it is quite a hard road for Ricoh and was more so with Pentax (has nothing to do with Asahi-beer or Ashahi which is just a name and means morning sun). I can't find this post anymore here in the forum, but a member once explained it pretty well.

Yes, business these days has changed a lot but the world has changed a lot. I am for finding solutions because it is so easy to fall for the Don Quijote trap... i.e. fighting what cannot be fought. Way to large for us.

So you have a great camera with your KP, it is not perfect, maybe ask the necessary questions with examples in the KP threads?
I sometimes love to take photos of birds and since I have the 55-300PLM I find AF with my KP very good but I am not the person to ask,
birds and moving objects never were that important for me.


If you still have your K30, then maybe repair it or get it repaired and then you have the AF you liked?
The K30 even can drive the KAF4 lenses with the 1.10 firmware!
I personally liked the AF of my K5IIs the most and found it the most ridicilous that Ricoh never offered a firmware update for KAF4 for the great K5 series. The K5 already is in some ways superior to the K30/50 and the the K5II for sure. Not to support those was a big big mistake because many customers found that too mean and stopped buying the new Pentax bodies, either stayed with their K5-series or ... sadly... swapped company.

Last edited by photogem; 07-24-2020 at 10:04 AM.
06-01-2020, 08:44 PM   #24
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QuoteOriginally posted by niels hansen Quote
I Mean the rate of af presicion.

My first KP was the first in Denmark, it came from Sweden I bought it because the K30 became unrealibel, did not know of the solenoid problems.
The problems were AF and batterilife. The camera was sent to Holland and was replaced under warrenty.
My experience with tke KP is not directly correlated to the soleonid scandale. It is reflections about the quality of Pentax - and probably others.
Cameras today are very sophisticated, maybe they are not sufficiently tested before launched
For the moment I am satsified witth the KP, exept the performence when taking spontaneous portraits of kids, where reliabel AF is essentiel. Being 77 years old MF is not realistic with the KP
BUT my experience with two defective Pentax Dslrs make me nervous. Will other problems occur - and when?
Talking with my freinds indicate that other brands are not better.
The Spotmatc from 68 is my lifebelt Two years ago it got a CLA.
What lenses are you using and how much do you depend on "isolation"?

Our daughters were born when I was in my early 30's - at a point when I was using my "Super Program", a manually focused camera. Honestly, I would have had a hard time focusing on them perfectly; little kids, especially our younger daughter, just move too fast, but I have always taken pictures with a "comfortable DOF" .... often an f-stop around f/8. Today I have a KP, which I almost always use with one of three lenses - a Sigma 10-20mm, a DA 18-135mm DC, and a DA 55-300mm PLM; you will notice that the latter two have in-lens focus motor, which I greatly prefer. I almost always use my KP around f/5.6 - f/11 also, and the pictures I take with that camera are always in focus - in 18 months I have never taken a photo with my KP that is out of focus. In general, I am extremely happy with my KP - I have no complaints of the quality that Pentax has put into that camera, so I am completely confused by your complaints.

BTW - the KP has less battery life than the K-3ii does, but everyone knows that - it has the same smaller battery that the K-50 does, but that has never been an issue for me, either the K-30 or the KP.

Last edited by reh321; 06-01-2020 at 09:18 PM. Reason: Punctuation
06-01-2020, 09:35 PM   #25
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I think this belongs now into a KP or different thread.
The KP doesn't use a solenoid but a stepper-motor.
06-01-2020, 10:07 PM   #26
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QuoteOriginally posted by niels hansen Quote
.. The actual KP is good - hope it lasts - if you can overlook the imprecise pdaf.
?

There should be no problem.

Have you done the microadjustments? If they require more than -10 or +10 you need to send the body back, its AF module is out of alignment.
06-02-2020, 01:10 PM - 2 Likes   #27
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QuoteOriginally posted by skolkmeier Quote
My ks2 was manufactured in May of 2017, and it failed as well.
As failing versions of the K-30 were returned for warranty service, Pentax realized they had a problem, and the modified design resulted. By this time, the K-S2 was ready for production. This design apparently was better, but the "green" solenoid was still a weak area, so some K-S2 and K-70 models still fail. Since this is a problem with aging, dealing with it is not easy, so I believe Pentax should just give up on it and use the stepper-motor based design on future cameras.

Last edited by reh321; 06-02-2020 at 01:19 PM. Reason: grammatical correction
06-06-2020, 08:09 AM - 1 Like   #28
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Just returned fro a sailing trip in my nordic folkboat without connection to the shore, I will thank for the answers.
photogem:
my daughter has lived in Japan for two years, I visited her and her impression was very much like yours, not always sympathetic. I have been in KP threads, and my conclusion is that I ask for too much concerning pdaf. . A repair of the K30 is practically impossible in Denmark, and I am afraid of doing it myself, even with help from the eccelent from k30 threads. I use it manually with m 42 lenses
reh 321
My lenses are: Sigma 10 -20, DA 35 f 2,4, Da 50 f 1,8, Sigma 70 f 2,8 macro and Tamron 70 - 300 macro. In portraits i prefer shallow DOF and thats where the pdaf not always is precise. When I use the smaller f stops like you do there is no problem.
The battery life with the Kp that was replaced under warrenty wafar below 100 poses without flash and LW
Clackers
All lenses are fine tuned. I have a resolution chart, takes a photo in live view and find the fine tune value that gives the same result as live view. It works fine.
Finally some reflections between the folkboat and Spotmatic.
The folkboat was designed in 1941, newer designs are bigger, faster and more comfortable, but when it comes to the handling in especially hard weather it is still second to none, it is a surviver . In a way I think the same about the old all metal cameras, like the spotmatic.
I forgot: one of the virtues of the KP is the eccelent exposure. I use the KP instead of my Spotmeter for analogue BW
07-24-2020, 10:55 AM - 1 Like   #29
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QuoteOriginally posted by niels hansen Quote
@photogem:
my daughter has lived in Japan for two years, I visited her and her impression was very much like yours, not always sympathetic.
Oh... but isn't nor was it my impression of the Japanese mentality at all!
I have met quite a few Japanese businessmen and usually met an amazing code of honor, a true sense of doing things right.
08-22-2020, 12:14 AM   #30
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New information added, but I am going to have this thread moved to the articles forum:
Pentax Articles | Pentax K-1 | Pentax K-5 | Pentax K-30 - PentaxForums.com
This thread is not only K30/50 related but for all Pentax bodies using a solenoid for aperture-control
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