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01-30-2016, 07:00 PM   #1
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Aperture Phantom strikes again - Pentax K50

Hello everyone,
It has been a lot written about the aperture problem on Pentax K30. I`ve recently got the same issue with my Pentax K50. The pictures are underexposed. It is ridiculous, it is a bright and sunny day and I have to shoot on ISO 800 and shutter 60 to get a normal picture. Basically the only thing I can shoot normally is a night scenery, because I use a tripod and Bulb mode with very long time of exposure.

I am pretty sad about it because I like my K50 but I cant use it. I would expect the company to provide free service for this issue because it is not users` fault. If I consider that the K50`s price on Australian market is around 550 AUD and the service costs around 200 AUD, it is almost better to throw the camera away and buy a new one. I dont really like that Pentax doesnt communicate this problem with its customers.

I dont want this to look like a rant on Pentax, I know that Nikon and Canon had kind of serious problems in their past too. I am pretty sad about that, I was planning to buy the new Pentax full frame camera no matter what, because I was fully satisfied with my K50, but now I feel cant trust the company.

I will be happy for any kind of response,

Vasi

01-30-2016, 07:46 PM   #2
pjv
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Hi vasi. Welcome aboard the forum. Sorry to hear you are having problems with your K-50. The K-50 and the Full Frame will be completely different animals, so I wouldn't worry too much. Many members here use the K-50 and will help you to check some things out. Good luck.

Last edited by pjv; 01-30-2016 at 07:47 PM. Reason: add text
01-30-2016, 08:03 PM   #3
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Frankly it sounds a bit odd and does not seem like a camera problem. If the camera can get the right exposure at iso 800, it should be able to at lower iso. Sounds more like the lens is not allowing a larger aperture. But even that is strange--bright day at iso 800 and 1/60 sec means lens is at about f/128 (which it should not be able to do).
01-30-2016, 09:14 PM   #4
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QuoteOriginally posted by dms Quote
Frankly it sounds a bit odd and does not seem like a camera problem. If the camera can get the right exposure at iso 800, it should be able to at lower iso. Sounds more like the lens is not allowing a larger aperture. But even that is strange--bright day at iso 800 and 1/60 sec means lens is at about f/128 (which it should not be able to do).
When the aperture control problem happens - most of the reports are of underexposure caused by the lens stopping down all the way all the time.

You can often use the camera and lens on manual mode successfully or with m42 lenses on AV mode. This is due to how the aperture mechanism works.

01-31-2016, 02:18 AM   #5
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QuoteOriginally posted by dms Quote
Frankly it sounds a bit odd and does not seem like a camera problem. If the camera can get the right exposure at iso 800, it should be able to at lower iso. Sounds more like the lens is not allowing a larger aperture. But even that is strange--bright day at iso 800 and 1/60 sec means lens is at about f/128 (which it should not be able to do).
It is definitely a camera issue because the photos are underexposed if I use any of my three Pentax lenses. It looks like the aperture lever on the lenses is not lifted by the camera mechanism.

---------- Post added 01-31-16 at 02:23 AM ----------

QuoteOriginally posted by UncleVanya Quote
When the aperture control problem happens - most of the reports are of underexposure caused by the lens stopping down all the way all the time.

You can often use the camera and lens on manual mode successfully or with m42 lenses on AV mode. This is due to how the aperture mechanism works.
I actually put a piece of plastic to block the aperture lever on the lens. It basically means that I have to shoot all the time as wide open as I can. For telephoto and 50 mm 1.8 prime lens it is a good solution, for wide angle lenses and shooting landscapes with f11 and higher it is problematic.
01-31-2016, 03:53 AM   #6
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Welcome to the forum, sorry to hear about your problems, I think you've just been unlucky as I've used Pentax products for years without any serious issues.
01-31-2016, 08:17 AM   #7
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Wait, you are jamming the auto-stop down lever so the lens remains wide open and you still get underexposure? If that's the case then the problem isn't with the aperture control block.

With the lenses as normal how does the diaphragm operate otherwise? Set the camera to manual with a slow shutter speed (or set to "B"). Then operate the shutter or DOF preview going through the range of f-stops while looking through the front of the lens. Does the iris operate as expected? Does it always close down the same no matter what f-stop is selected?
01-31-2016, 02:21 PM   #8
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G'day mate and welcome to the forum

04-08-2016, 08:09 PM   #9
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QuoteOriginally posted by Not a Number Quote
Wait, you are jamming the auto-stop down lever so the lens remains wide open and you still get underexposure? If that's the case then the problem isn't with the aperture control block.

With the lenses as normal how does the diaphragm operate otherwise? Set the camera to manual with a slow shutter speed (or set to "B"). Then operate the shutter or DOF preview going through the range of f-stops while looking through the front of the lens. Does the iris operate as expected? Does it always close down the same no matter what f-stop is selected?
Hi, no, I am getting the underexposed photos in normal setting. The diaphragm doesn`t work at all, I shoot with f22 regardless what aperture I set up. So I had to block the ever manually to keep the diaphragm as wide open as possible.
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