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Dark exposure problems on K-30 or K-50? Read me first!
Posted By: MarkJerling, 07-15-2018, 04:02 AM

Original post by Auzzie-Phoenix. Dark exposure problems on K-30 or K-50? Discussion Thread - PentaxForums.com

The following's Auzzie-Phoenix's original post, copied here in it's entirety.
Hello everyone,

Occasionally people create new threads about their K-30 or K-50 taking dark exposures. In the interest of reducing the amount of new threads regarding the matter, I have decided to create a step-by step tutorial on the matter, albeit without any images so hope people are good with written instruction. There does tend to be an issue with some (not all) K-30 and K-50 cameras, where they take dark frames, and will require professional service either by warranty or out of warranty paid repair. This issue is known as aperture block failure. While the issue does seem to be more of a WHEN rather than an IF situation, not all dark exposure problems are caused by this issue, so no need to get prematurely paranoid about it. The goal of this tutorial is not to unnecessarily upset anyone, or discourage purchases of K-30/K-50 units (my aperture block failed in my K-50, and while I find it sad I do still use the K-50 in a limited capacity and definitely love the camera), the purpose of this tutorial is to help you diagnose possible aperture block failure in your camera, without the need to create a new thread about it.

What you will need:

1.) Possibly defective K-30/K-50 unit.
2.) A lens that has an aperture ring with an "A" setting. Or kit lens and some other manual lens with aperture ring.
3.) A few moments of your time.

As you can see, there isn't a lot required for this test, and it only takes a few minutes to perform. For the test, you will want to be in an area with adequate lighting, after all... what's the point of doing this test if you're in a dark room?
We'll do 3 different routes, one for people with lenses that have focus rings with an "A" setting, one for those without who have to use 2 separate lenses, and finally one for people who do not have any lenses with aperture rings. Please bear in mind that some instances of aperture failure can be intermittent. Intermittent failure can be caused by the motor working at some times and not working others, but it WILL eventually degrade to a constant failure state over time.

For those with lenses that have the "A" setting on an aperture ring-

Step 1:

a.) Mount the lens on the camera.
b.) Set aperture ring to "A" setting.
c.) Take a picture.
d.) Set aperture ring to an aperture value that should take a properly exposed image.
e.) Take a 2nd picture.
f.) Examine both exposures.

If the image you took when the aperture ring was set to "A" is severely underexposed (dark exposure), and the image you took with the aperture ring set to a specific value is NOT underexposed, you more than likely have aperture block failure in your unit. If BOTH exposures are dark, this could indicate a more severe problem with the unit, or there may be an issue with the lens. To rule out lens issues, try again with a different lens. Should the second lens replicate both images with dark exposures, then it might be an issue with the light meter sensor, or the image sensor.

For those who do not have a lens with "A" setting on an aperture ring (such as the kit lens)-

Step 1:

a.) Mount first lens (without aperture ring) to the camera.
b.) Set camera settings to what will supposedly create a proper exposure.
c.) Take a picture.
d.) Turn off unit and swap to manual lens.
e.) Set aperture on lens with aperture ring to an appropriate aperture value.
f.) Take another picture.
g.) Examine both exposures.

As with the previous route for those with the "A" setting, we need to examine the exposures that you took with each lens. If the exposure taken with the lens that did not have an aperture ring is dark, and the exposure taken with the lens with the aperture ring is normal, you may have aperture block failure.

For those who do not have a lens with an aperture ring-

Step 1:

a.) Mount lens to camera.
b.) Set aperture setting in camera to a value where the lens iris will be fairly open upon shutter release.
c.) Look down into lens while under decent lighting, and press shutter button.
d.) Note whether iris opens up or stays narrow.

If during your testing, the aperture iris did not widen, then you more than likely have aperture block failure. You are free to try this with multiple lenses to rule out lens issues.

Step 2: (this step is for everyone from any of the above step paths)

Upon determining that aperture block failure is the most likely cause of your problem, determine whether or not it is feasible to be repaired, or if replacing the unit will be the more cost effective option. Those who are still covered under warranty should most definitely send the unit in for repair. Those out of warranty have a difficult choice ahead of them. In my case, my k-50 aperture block failed outside of warranty. To have it repaired would have cost almost as much as a brand new in box body. I eventually relegated the k-50 to alternate/crippled usage, and purchased a K-3II as my new primary body. Not all people decide to opt for the solution I ultimately took. Several do spend the money to have the unit repaired. The choice is completely up to you.


This concludes my very brief tutorial on testing for aperture block failure in the K-30/K-50. I hope you checked here first before starting a new thread on the subject, and that you found the information here useful. If enough people consider the tutorial to be helpful, please suggest that this become a sticky topic, so that it doesn't become lost in the ever-revolving shuffle of forum topics.


Last edited by MarkJerling; 07-15-2018 at 04:08 AM.
Views: 1,699
07-15-2018, 08:17 PM   #2
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