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05-20-2013, 07:25 AM   #16
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Am I missing something? The bad aperture mechanism (in lens) should only introduce the evenly underexposed pictures. Here I see that something is blocking the sensor. Something like slow mirror.

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05-20-2013, 12:12 PM   #17
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Thanks for the feedback. I tried a few things based on what you suggested. I completely charged the original battery and mounted the DA-L 18-55mm AL wide open (f3.5). The setting was P mode (Tv hyper). Same thing happened again al 1/5000 and 1/6000 (see image). I'm guessing it's a mirror problem. Since we don't have Pentax Service around here I'll just will have to avoid higher speeds...

Last edited by Dr.Pentaxian; 05-24-2013 at 11:12 AM.
05-21-2013, 01:39 PM   #18
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Oh well, the OP apparently has disappeared...I guess we will never know!!!


Steve
05-21-2013, 09:51 PM   #19
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Steve, he hasn't been gone that long... some of us do have to work for a living

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05-24-2013, 07:58 AM   #20
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QuoteOriginally posted by pavpen Quote
Am I missing something? The bad aperture mechanism (in lens) should only introduce the evenly underexposed pictures. Here I see that something is blocking the sensor. Something like slow mirror.

Cheers
Remember that at speeds faster than the X-sync speed, the shutter operates as a moving slit. If the light intensity changes as the slit moves, you will get a gradient effect.

As for the mirror...it has been my understanding that most shutter systems are integrated into the mirror box such that the shutter travel does not start until after the mirror is confirmed in the up position. Conversely, the mirror does not fall until after the following curtain finishes its travel. At least that is how they used to make them. Things may be different now with the requirement for high FPS drive rates.

A good check would be to use the 2s delay or self-timer mechanism to take the mirror out of the loop.


Steve
05-24-2013, 08:42 AM   #21
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If it helps, I just tried my K-30 with a few old lenses, K55/1.8, A50/1.7, M135/3.5, Vivitar 28/2.8 in M, Av modes at f8 and wide open and couldn't see any issues at all at 1/6000sec.
05-24-2013, 10:38 AM   #22
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QuoteOriginally posted by stevebrot Quote
A good check would be to use the 2s delay or self-timer mechanism to take the mirror out of the loop.
Thanks Steve, I'll try it and post the results.
05-24-2013, 11:07 AM   #23
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I followed Steve's suggestion and tried it with the 2s delay. Mode M, M-50mm lens wide open (f1.7) at 1/5000s. This is what I got...

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05-24-2013, 03:11 PM   #24
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QuoteOriginally posted by Dr.Pentaxian Quote
I followed Steve's suggestion and tried it with the 2s delay. Mode M, M-50mm lens wide open (f1.7) at 1/5000s. This is what I got...
Well, there you go. Wide open, M-mode, mirror up, nothing left to blame but the shutter.

Hello, Pentax? We have a problem...

It is still on warranty, I hope



Steve
05-24-2013, 04:20 PM   #25
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Did you try a different battery?

My same issue cleared up when I tossed the lousy batteries I was using and reverted to the kit battery and better quality AA's.
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