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04-29-2011, 03:47 PM   #1
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Extremely dark pictures from k-x, wasn't like this before

Hi

My camera is broken today. The pictures it takes suddenly gone very dark, so dark that unless I have >1 sec exposure or point to it at a strong light or sun, all you can see is black color on both PC and LCD of the camera.

Even at ISO 12800 doesn't help at normal AE metering settings. AE metering showing what should have been correct exposure settings at +0EV will produce pictures completely pitch dark. I am not a beginer at photography and I can assure you this haven't happened before. It started happening today after I changed lens.

Now, I have tried both lens from the official kit, the 18-55mm and 55-200mm. Both have the same problem now. I have tried perform general cleaning on the lens and CCD sensor, I don't see anything wrong with it.

Changing ISO settings have an effect, so the setting is working. Changing shutter speed also works. One thing I can't verify is the apecture ring. Looking into the lens when I press the shutter, F4 and F22 looks the same size to me but I am not sure. Maybe somehow it's stuck at apecture setting? Nevertheless the picture can't be that dark surely.

Video works quite well though through the lens. If I take lens away and just perform naked CMOS shot, it comes out completely white.

I don't get this at all.
Any ideas?

Thanks very much


Last edited by mobiuspizza; 04-29-2011 at 03:54 PM.
04-29-2011, 03:57 PM   #2
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Welcome to the forum.
Firstly, you must have the 50-200 (Pentax doesn't have a 55-200) and the K-x sensor is a CMOS (not a CCD). Secondly, are you sure the lens is wide open when mounted on the camera before the shutter has been released? If you're not sure, unmount the lens and gently depress the diaphragm lever to see how free/stiff it is. Next, what mode are you in - if you're in manual mode, there is the possibility you're not allowing the camera to meter.

Put your camera in a green mode and try again, ensuring a fresh set of batteries and new SD card - then post some examples here for even more useful assistance.
04-29-2011, 04:25 PM   #3
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Thanks you are correct.
I did not use the manual mode. Any other mode produces the same result.

Sadly I went to delete the problem pictures just after the problem started.

I attached two photos.

The one with the woodpecker, is taken with manual mode, after auto picture mode produced pitch dark pictures. I increased ISO setting to compesate.

ISO6400 on a relatively bright situation, with 1/30 shutter speed at F4.5. At any normal situation using such a high ISO value, the image should have been white washed.

The other photo is me just now taking a picture of my ceiling lamp. I intentionally put the focus next to it instead of directly since AE was going to set my shutter speed to 1/1500 if I aim directly. With 1/180 even with F4.5, the picture as you can see is completely underexposed. This is abnormal as the lamp is bright and such a setting as suggested by AE is very reasonable.
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04-29-2011, 04:30 PM   #4
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QuoteOriginally posted by mobiuspizza Quote
Looking into the lens when I press the shutter, F4 and F22 looks the same size to me but I am not sure.
Still shooting in the dark (yes, pun intended) here....

Is "the same size" fully open or fully close? Put the camera in M mode and choose a low shutter speed (e.g. 1/4 sec), you should be able to tell.

Also, does the viewfinder appear darker than normal?

Do you have any lens with aperture ring? If yes, mount the lens on to the camera, change the aperture by rotating the aperture ring. Is the aperture fully opened or does it open/close with the aperture ring?

04-29-2011, 04:32 PM   #5
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I've clarify in that post that I've tried all camera modes, reseting custom function settings.

Batteries are fresh, I have just changed it. I even updated firmware from 1.01 to 1.02. I don't have a new set of SD card, but that shouldn't be the problem. Without the card this issue still present using digital preview.

Diaphragms on the lens are not stiff. The fact that both lens kit exhibit this problem makes it unlikely that it's the lens. The diapraghm is fully open until the shutter is released.This I have visually checked by just looking into the lens from front.

Last edited by mobiuspizza; 04-29-2011 at 04:43 PM.
04-29-2011, 04:37 PM   #6
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QuoteOriginally posted by SOldBear Quote
Still shooting in the dark (yes, pun intended) here....

Is "the same size" fully open or fully close? Put the camera in M mode and choose a low shutter speed (e.g. 1/4 sec), you should be able to tell.
That's what I did, when shutter is on, the apecture diaphragm closes like an iris and retain a smaller hole for light to go in. Correct me if I am wrong. I think the size of the hole is determined by F stop settings. To be honest I cannot tell the difference for the size of the hole between F4 and F22, for both lens.

QuoteOriginally posted by SOldBear Quote
Also, does the viewfinder appear darker than normal?
Completely normal, as with video mode.

QuoteOriginally posted by SOldBear Quote
Do you have any lens with aperture ring? If yes, mount the lens on to the camera, change the aperture by rotating the aperture ring. Is the aperture fully opened or does it open/close with the aperture ring?
Nopes

Last edited by mobiuspizza; 04-29-2011 at 04:43 PM.
04-29-2011, 04:46 PM   #7
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QuoteOriginally posted by mobiuspizza Quote
The one with the woodpecker, is taken with manual mode, after auto picture mode produced pitch dark pictures. I increased ISO setting to compesate.
Seeing the auto version would be more useful here.

QuoteQuote:
The other photo is me just now taking a picture of my ceiling lamp. I intentionally put the focus next to it instead of directly since AE was going to set my shutter speed to 1/1500 if I aim directly. With 1/180 even with F4.5, the picture as you can see is completely underexposed.
??? It's a picture of a light bulb. Looks perfectly exposed to me - any more exposure and the light bulb would have been blown out. Just because you apparently wanted it to be a picture of the ceiling doesn't mean the camera can read your mind. If you include a light source in the image, the camera will try to expose accordingly. Moving the light source off center doesn't really change this, unless you shoot in spot metering mode.

Seeing EXIF would also be useful. But taking your description of the exposure settings at face value, it does sound like you either aren't getting the aperture or shutter speed you think you are - and that might be a camera problem.
04-29-2011, 04:49 PM   #8
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Try a long exposure (more than a second) shot in Manual focus at f22. While you press the shutter button, hold the camera backwards so you are looking at the lens front and hold the camera so the viewfinder is facing a light source. You should see the aperture stop down during the exposure. Let's verify the aperture mechanism is working before pulling the other usual stuff out of our collective ass.

(at ISO 12800, it shouldn't matter what aperture you're using unless you are actually shooting into the dark with a fast shutter speed).



04-29-2011, 04:54 PM   #9
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QuoteOriginally posted by mobiuspizza Quote
...when shutter is on, the apecture diaphragm closes like an iris and retain a smaller hole for light to go in. Correct me if I am wrong. I think the size of the hole is determined by F stop settings. To be honest I cannot tell the difference for the size of the hole between F4 and F22, for both lens.
I still hope the problem is mechanical. If it is, there's a better chance you can fix it without sending it to Pentax. If it is electronic, there's not much we can do.

Here's "normal":

- When off camera, a lens that has no aperture ring has the aperture fully close (the opening is small).

- When attached to the camera, the aperture opens up fully, and closes down to the set aperture during taking the photo, and opens up again.

Now to determine if the aperture and the aperture linkage work correctly:

- Attach the lens to the camera. Set it to manual mode with a low shutter speed, e.g. 1/4 sec..

- Turn the camera so that the viewfinder faces a light source so it's easy to see the aperture opening from the front of the camera.

- On the camera, set the aperture to max (e.g. F/4).

- Hit the shutter release while looking into the front of the lens. You should see no movement of the aperture because it remains fully opened.

- Set the aperture to min (e.g. F/22).

- Hit the shutter release while looking into the front of the lens. You should see the aperture close down, then open up again at the end for the exposure.

Please report back.
04-29-2011, 04:56 PM   #10
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QuoteOriginally posted by Marc Sabatella Quote
Seeing the auto version would be more useful here.



??? It's a picture of a light bulb. Looks perfectly exposed to me - any more exposure and the light bulb would have been blown out. Just because you apparently wanted it to be a picture of the ceiling doesn't mean the camera can read your mind. If you include a light source in the image, the camera will try to expose accordingly. Moving the light source off center doesn't really change this, unless you shoot in spot metering mode.

I can send you many many picutres of auto mode of anything I take. None of it will be correctly exposed. The AE metering is telling the correct settings to use, but the image that comes out somehow is not.

I've been under the sun today, taking auto-mode pictures all the time. that was outdoor. All the picture which came out were completely dark. Getting pitch dark pictures outdoor under the sun even with auto mode I can assure you is abnormal, and I have never seen anything like it. It's not the first time I take pictures. I know from experience that 1/150 at ISO400 is correct exposure for this amount of lighting.
All 3 AE metering mode I have tried, same effect

Now I will take one of my PC monitor, auto mode, relatively bright but my room light is also on so it's a normal situation.
AE tells me use 1/250:

As you can see below, pitch dark. I can honestly tell you this is what happens when I photograph outdoor under the sun as well.
No my lens cap wasn't on :P
Attached Images
 

Last edited by mobiuspizza; 04-29-2011 at 05:09 PM.
04-29-2011, 05:05 PM   #11
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QuoteOriginally posted by SOldBear Quote

- Hit the shutter release while looking into the front of the lens. You should see no movement of the aperture because it remains fully opened.

- Set the aperture to min (e.g. F/22).

- Hit the shutter release while looking into the front of the lens. You should see the aperture close down, then open up again at the end for the exposure.

Please report back.
The same behavior happens in both F-stop settings... The apecture remains fully open just before I press shutter release, then a diaphragm closes for 1/4 sec and opens up again. The size of the closed down apecture is the same as far as naked eye can judge...

The apecture closes if lens is unscrewed from camera

Thanks for the help from everyone so far, I am off to bed and I will investigate more tomorrow.
04-30-2011, 05:26 AM   #12
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Bright sunshine outside, using auto mode:
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04-30-2011, 05:34 AM   #13
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I think you said you've done a custom menu reset, but did you also try a camera reset pg 276.
04-30-2011, 05:46 AM   #14
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QuoteOriginally posted by DanWeso Quote
I think you said you've done a custom menu reset, but did you also try a camera reset pg 276.
Done that just now, no help.

If I use LV before taking picture, strangely the pictures are brighter, but still not good enough
04-30-2011, 09:49 AM   #15
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If the closing of the aperture blades are the same at f/22 and f/4 that is probably the issue. As stated by soldbear they should be different. It sounds like it is always stepping down to the smallest aperture it can. That would give dark pictures even in daylight at fast speeds.

Since you said it started when you changed lens I would suspect dirt on the contacts or something like that. Clean the contacts. I don't have a k-x but I would look to see if a contact button has been pushed in to far or popped out.

There should be a big difference between f/4 and f/22.
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